Q60. Why is the work done by gravity negative while a body is being lifted?
[RRB Group D — 18 Aug 2026, Shift 2]
(A) Gravity does positive work only in a fall
(B) The net force must be zero
(C) The magnitude of gravity changes
(D) The displacement is upward while gravity acts downward
Answer: (D) The displacement is upward while gravity acts downward
Explanation: Work is the scalar product of force and displacement. Lifting moves the body upward, whereas its gravitational force points downward. Their angle is 180 degrees, so W = Fs cos 180° is negative.
Q59. Why does a flat sheet of paper fall more slowly than a stone in air?
[SSC GD Constable — 26 May 2026, Shift 3]
(A) The objects experience different gravitational acceleration
(B) The paper encounters greater air resistance
(C) Only the difference in shape is relevant
(D) Gravity does not act on paper
Answer: (B) The paper encounters greater air resistance
Explanation: Air drag opposes the downward motion and has a larger effect relative to the weight of a flat sheet. In a vacuum, absent air resistance, a paper sheet and stone would have the same gravitational acceleration.
Q58. At the instant a body starts falling freely from rest at height h, which energy pair is correct?
[SSC GD Constable — 26 May 2026, Shift 3]
(A) Potential energy = 0; kinetic energy = mgh
(B) Potential energy = mgh; kinetic energy = 0
(C) Potential energy = ½mv²; kinetic energy = mgh
(D) Both potential and kinetic energy are zero
Answer: (B) Potential energy = mgh; kinetic energy = 0
Explanation: With the ground as the reference level, the elevated body has gravitational potential energy mgh. Because the fall starts from rest, speed is initially zero and kinetic energy is zero. During descent potential energy turns into kinetic energy.
Q57. Which kind of motion describes free fall near Earth when air resistance is ignored?
[RRB NTPC Graduate CBT-I — 17 Mar 2026, Shift 1]
(A) Uniformly accelerated motion
(B) Uniform motion
(C) Motion without acceleration
(D) Periodic motion
Answer: (A) Uniformly accelerated motion
Explanation: Near the surface, gravitational acceleration is nearly constant at about 9.8 m/s². Consequently, a freely falling body changes its velocity by equal amounts in equal intervals. That is uniformly accelerated motion, not motion at constant speed.
Q56. Taking upward as positive, what sign is used for acceleration in a vertically upward throw?
[RRB Technician Grade III — 06 Mar 2026, Shift 1]
(A) Negative
(B) Positive because gravity is constant
(C) Positive because the body rises
(D) The sign is unrelated to the chosen axis
Answer: (A) Negative
Explanation: The gravitational acceleration always points downward near Earth. If upward is designated the positive direction, downward acceleration is represented by −g. This sign convention yields v = u − gt and explains why the rising body slows down.
Q55. A stone falls freely from rest. Its motion is classified as which of these?
[RRB Group D — 05 Feb 2026, Shift 2]
(A) Non-uniform motion
(B) Straight-line motion with constant speed
(C) Motion with zero acceleration
(D) Uniform-velocity motion
Answer: (A) Non-uniform motion
Explanation: The stone travels increasingly large distances during successive equal time intervals because gravity increases its downward speed. Hence its speed is not uniform, although the downward acceleration is approximately constant in the near-surface region.
Q54. Assess the statements:
(i) g depends on the mass of the falling object;
ii) g is identical everywhere in the universe.
[RRB Group D — 04 Feb 2026, Shift 3]
(A) Only statement (i) is true
(B) Only statement (ii) is true
(C) Neither statement is true
(D) Both statements are true
Answer: (C) Neither statement is true
Explanation: The acceleration g depends on the attracting celestial body and the observation point, not the mass of the object being dropped. Since planetary masses and radii differ, gravity is not universally identical. Both proposed statements are therefore false.
Q53. Which formula expresses surface gravity using planetary mass M, radius R and universal constant G?
[RRB Group D — 04 Feb 2026, Shift 2]
(A) g = GR/M²
(B) g = R²/(GM)
(C) g = GM/R
(D) g = GM/R²
Answer: (D) g = GM/R²
Explanation: Newton’s gravitational law gives F = GMm/R² for a mass m on the surface. Newton’s second law gives F = mg. Equating and cancelling m produces g = GM/R², which decreases when the radius increases.
Q52. Just before a freely falling body reaches the ground, which energy condition applies?
[RRB Group D — 04 Feb 2026, Shift 1]
(A) Potential energy is maximum and kinetic energy minimum
(B) Potential and kinetic energies must be equal
(C) Kinetic energy is maximum and potential energy minimum
(D) Both energies necessarily become zero
Answer: (C) Kinetic energy is maximum and potential energy minimum
Explanation: Ignoring drag, the loss of gravitational potential energy equals the gain in kinetic energy. Close to ground level the body has its greatest speed and therefore maximum kinetic energy, while potential energy relative to the ground is lowest.
Q51. A planet has twice Earth’s mass and twice Earth’s radius. What is its surface gravitational acceleration?
[RRB Group D — 03 Feb 2026, Shift 2]
(A) 2g
(B) g/4
(C) g
(D) g/2
Answer: (D) g/2
Explanation: Surface gravity varies as M/R². With mass changing to 2M and radius to 2R, the new acceleration becomes G(2M)/(2R)² = GM/(2R²), precisely half Earth’s surface gravitational acceleration g.
Q50. Consider a ball thrown vertically upward:
(1) its upward velocity decreases at rate g;
(2) gravity remains downward.
[RRB Group D — 08 Jan 2026, Shift 3]
(A) Both statements are false
(B) Only statement 2 is true
(C) Only statement 1 is true
(D) Both statements are true
Answer: (D) Both statements are true
Explanation: While rising, the ball has upward velocity but downward gravitational acceleration. Therefore the upward velocity steadily decreases by about g each second. At its highest point velocity is momentarily zero, yet acceleration still acts downward.
Q49. Which statement about potential energy is correct?
[RRB Group D — 14 Dec 2025, Shift 1]
(A) It is always zero on the ground
(B) Its value can be negative relative to a chosen reference
(C) It never converts into kinetic energy
(D) It depends solely on mass
Answer: (B) Its value can be negative relative to a chosen reference
Explanation: Gravitational potential energy near the surface can be written mgh, with h measured from an arbitrarily chosen zero level. A position below that level has negative h and negative relative potential energy. Energy differences, rather than its chosen zero, determine motion.
Q48. When gravitational potential energy becomes kinetic energy in free fall, what happens to total energy?
[RRB Group D — 10 Dec 2025, Shift 1]
(A) Total energy remains constant
(B) Energy disappears from the system
(C) Total mechanical energy must increase
(D) New energy is continuously created
Answer: (A) Total energy remains constant
Explanation: For ideal free fall without air resistance, gravitational potential energy decreases while kinetic energy increases by exactly the same amount. Their sum, mechanical energy, remains constant; this illustrates conservation of energy rather than energy creation or destruction.
Q47. For an object dropped straight down and falling freely, what happens to its direction of motion?
[RRB Group D — 08 Dec 2025, Shift 3]
(A) It becomes horizontal
(B) It turns continuously
(C) It points opposite to gravity
(D) It remains downward
Answer: (D) It remains downward
Explanation: An object dropped vertically from rest, with no horizontal velocity and no air force, accelerates toward Earth’s centre. Its speed increases, but its downward direction does not change. This assumes the local gravitational field is approximately vertical.
Q46. For an object projected vertically upward, which direction does gravitational acceleration take while it rises?
[RRB Group D — 08 Dec 2025, Shift 2]
(A) Along the upward motion
(B) Zero at the peak
(C) Opposite the upward motion
(D) Always increasing upward
Answer: (C) Opposite the upward motion
Explanation: Gravity points toward Earth’s centre, so during ascent it acts opposite to the body’s upward velocity. That downward acceleration reduces the upward speed until the highest point. Even at the top, acceleration remains downward rather than vanishing.
Q45. As a body falls freely from height, into which form is its gravitational potential energy converted?
[RRB Group D — 04 Dec 2025, Shift 1]
(A) Sound energy
(B) Thermal energy
(C) Chemical energy
(D) Kinetic energy
Answer: (D) Kinetic energy
Explanation: As the descending body loses altitude, its gravitational potential energy mgh decreases. In ideal free fall, this energy appears as increased kinetic energy ½mv². Mechanical energy is conserved provided air drag and other dissipative effects are neglected.
Q44. A body is dropped from rest for 3 s with g = 10 m/s². What downward velocity does it attain?
[RRB Group D — 27 Nov 2025, Shift 1]
(A) 20 m/s
(B) 30 m/s
(C) 10 m/s
(D) 40 m/s
Answer: (B) 30 m/s
Explanation: For constant acceleration, final velocity is v = u + gt. Since the object is released from rest, u = 0. Substituting g = 10 m/s² and t = 3 s gives v = 30 m/s downward.
Q43. As an object falls freely, how do its potential energy and kinetic energy change?
[SSC CHSL Tier-I — 22 Nov 2025, Shift 3]
(A) Both decrease
(B) Both increase
(C) Potential decreases, kinetic increases
(D) Potential increases, kinetic decreases
Answer: (C) Potential decreases, kinetic increases
Explanation: Height decreases throughout descent, reducing gravitational potential energy mgh. Meanwhile, gravity accelerates the object and increases its speed, raising ½mv². If no dissipative force acts, the lost potential energy exactly equals the gained kinetic energy.
Q42. Judge two statements: I. Weight has magnitude only. II. Weight acts vertically downward.
[SSC CHSL Tier-I — 14 Nov 2025, Shift 1]
(A) Only I is correct
(B) Only II is correct
(C) Both are correct
(D) Neither is correct
Answer: (B) Only II is correct
Explanation: Weight is the gravitational force on a body, W = mg. A force has both magnitude and direction, so statement I is wrong. Near Earth’s surface the direction is toward Earth’s centre, approximately vertically downward, validating statement II.
Q41. A ball goes vertically upward at 10 m/s. With g = 9.8 m/s², what maximum height does it reach?
[SSC CGL — 25 Sep 2025, Shift 2]
(A) 1.02 m
(B) 5.10 m
(C) 10.2 m
(D) 20.4 m
Answer: (B) 5.10 m
Explanation: At the top the ball’s instantaneous velocity is zero. Using v² = u² − 2gh gives h = u²/(2g) = 100/19.6, approximately 5.10 m. This neglects air resistance and measures height above the launch point.
Q40. Which statement about work done by gravity is incorrect?
[UPSC NDA-II GAT — 14 Sep 2025]
(A) It is independent of the path
(B) It depends on vertical separation of endpoints
(C) It depends on the route followed
(D) It is zero for horizontal displacement
Answer: (C) It depends on the route followed
Explanation: Gravity is a conservative force. In a nearly uniform field its work is mg times the downward change in height, irrespective of the route. A purely horizontal displacement produces zero gravitational work; path dependence is therefore the incorrect claim.
Q39. Two unequal-mass bodies are released together from a tower. Ignoring drag, which quantity is equal for them at each instant?
[UPSC NDA-I GAT — 13 Apr 2025]
(A) Momentum
(B) Acceleration
(C) Potential energy
(D) Kinetic energy
Answer: (B) Acceleration
Explanation: Both bodies are subject to the same local gravitational acceleration g. Momentum and energies contain their differing masses and generally differ. When released at the same time, each gains the same speed, even though their masses are unequal.
Q38. How does g at Earth’s poles compare with g at the equator?
[RRB Technician Grade III — 28 Dec 2024, Shift 3]
(A) It is negative at the equator
(B) It is greater at the equator
(C) It is equal at both
(D) It is greater at the poles
Answer: (D) It is greater at the poles
Explanation: Earth’s flattened shape places the poles nearer the centre. Rotation also reduces effective gravity most at the equator. These effects together make surface gravitational acceleration slightly higher at the poles than at the equator.
Q37. A body is thrown upward. How is the direction of gravity related to its motion during ascent?
[RRB Technician Grade III — 28 Dec 2024, Shift 2]
(A) In the same direction
(B) Gravity is zero
(C) Opposite to its motion
(D) Gravity always follows its motion
Answer: (C) Opposite to its motion
Explanation: Although the body initially travels upward, gravity always pulls toward Earth’s centre. Its downward force reduces upward velocity. The body momentarily stops at the top, and then begins accelerating downward under the same gravitational force.
Q36. What force accelerates an object that falls toward Earth?
[RRB Technician Grade III — 28 Dec 2024, Shift 1]
(A) An outward repulsive force
(B) Earth’s gravitational attraction
(C) Nuclear force
(D) Electromagnetic force
Answer: (B) Earth’s gravitational attraction
Explanation: A freely falling object is pulled earthward by gravitational force. Newton’s second law converts that force into acceleration. Near Earth’s surface, the acceleration is approximately 9.8 m/s² if resistive forces such as air drag are negligible.
Q35. Compared with Earth, what happens to the weight of a body on the Moon?
[RRB Technician Grade III — 27 Dec 2024, Shift 3]
(A) It depends on body density alone
(B) It becomes smaller
(C) It becomes greater
(D) It remains equal
Answer: (B) It becomes smaller
Explanation: The Moon’s surface gravitational acceleration is about one-sixth of Earth’s. Since weight equals mass multiplied by local g, the same body weighs much less on the Moon. Its mass, however, remains unchanged during the transfer.
Q34. How does the near-surface gravitational acceleration of an object depend on its own mass m?
[RRB Technician Grade III — 26 Dec 2024, Shift 2]
(A) It is independent of m
(B) It varies as m²
(C) It varies inversely as m
(D) It is directly proportional to m
Answer: (A) It is independent of m
Explanation: Equating gravitational force GMm/R² to inertial force ma cancels the falling mass m and gives a = GM/R². Thus, in the absence of air drag, objects of different masses fall with the same local acceleration.
Q33. At what stage of a body’s free fall from height h is kinetic energy the largest?
[RRB Technician Grade III — 24 Dec 2024, Shift 2]
(A) After one-quarter of the distance
(B) Immediately after release
(C) After half the distance
(D) Immediately before impact
Answer: (D) Immediately before impact
Explanation: A falling body accelerates downward and gains speed throughout its descent. Kinetic energy depends on the square of speed, so it grows as the body approaches the ground. Without air resistance, it is greatest immediately before impact.
Q32. Which listed equation correctly relates initial and final velocity in uniform acceleration?
A: s = ut + 2at²;
B: v = u + ½at;
C: v − u = at.
[RRB Technician Grade III — 23 Dec 2024, Shift 2]
(A) Both B and C
(B) Only C
(C) Both A and B
(D) Only A
Answer: (B) Only C
Explanation: Acceleration is the rate of change in velocity. For constant a, a = (v − u)/t, so v − u = at. The other given relations use incorrect factors of acceleration and do not match standard kinematic equations.
Q31. An astronaut in the orbiting space station feels weightless. What quantity is zero?
[UPSC NDA-II GAT — 01 Sep 2024]
(A) Astronaut’s acceleration
(B) Normal reaction from the station floor
(C) Gravitational attraction of Earth
(D) Earth’s centripetal acceleration
Answer: (B) Normal reaction from the station floor
Explanation: Astronaut and station are both in continuous orbital free fall, accelerating under gravity together. Thus the floor exerts essentially no supporting normal force on the astronaut. Earth’s gravitational pull and the orbital centripetal acceleration are not zero.
Q30. When a stone is thrown upward, which energy conversion predominantly occurs during the ascent?
[SSC MTS — 12 Sep 2023, Shift 3]
(A) Kinetic energy into unspecified mechanical energy
(B) Potential energy into gravitational energy
(C) Mechanical energy into kinetic energy
(D) Kinetic energy into gravitational potential energy
Answer: (D) Kinetic energy into gravitational potential energy
Explanation: As the stone rises against gravity, its speed decreases and so does its kinetic energy. Its height and gravitational potential energy increase. Under ideal conditions, total mechanical energy remains constant while kinetic energy converts into potential energy.
Q29. As a body falls from a height, which of these quantities remains uniform?
[UPSC CDS-II General Knowledge — 04 Sep 2022]
(A) Acceleration
(B) Momentum
(C) Kinetic energy
(D) Potential energy
Answer: (A) Acceleration
Explanation: Assuming air resistance can be ignored and the fall is close to Earth’s surface, gravitational acceleration g is approximately constant. Momentum and kinetic energy increase as speed rises, while potential energy decreases with height.
Q28. Which dimensionless number is especially associated with gravitational forces in fluid motion?
[MPPSC Assistant Engineer Mechanical — 03 Jul 2022]
(A) Froude number
(B) Mach number
(C) Weber number
(D) Euler number
Answer: (A) Froude number
Explanation: The Froude number compares inertial effects with gravity in flowing fluids: Fr = V/√(gL), where L is a characteristic length. It is relevant to gravity-driven free-surface motion such as open-channel flow, waves and spillways.
Q27. Lifting an object, an army parade and a vertically falling object exemplify which type of motion?
[SSC CHSL 2021 Paper — 01 Jun 2022, Shift 2]
(A) Rectilinear motion
(B) Periodic motion
(C) Rotational motion
(D) Oscillatory motion
Answer: (A) Rectilinear motion
Explanation: These examples involve motion along a straight line, whether vertical or horizontal, and thus are rectilinear. A falling object may have changing speed, but its trajectory can still be straight. Uniform speed is not essential for rectilinear motion.
Q26. Which is NOT an example of projectile motion?
[SSC JE Mechanical — 22 Mar 2021, Evening]
(A) A stone thrown into the air
(B) A stone launched horizontally from a roof
(C) A car moving straight on a road
(D) A bullet fired from a gun
Answer: (C) A car moving straight on a road
Explanation: A projectile moves after launch primarily under gravity, following a curved trajectory in the ideal model. A car driving on a road is propelled and constrained by contact forces, so its straight-line motion is not projectile motion.
Q25. A 60 kg man has an apparent mass reading of 54 kg in a downward-accelerating lift. What is the lift acceleration?
[UPPSC Assistant Engineer Mechanical — 13 Dec 2020]
(A) 1.26 m/s²
(B) 1.98 m/s²
(C) 0.98 m/s²
(D) 1.76 m/s²
Answer: (C) 0.98 m/s²
Explanation: The scale force is N = m(g − a). A reading equivalent to 54 kg gives 54g = 60(g − a). Therefore a = (1 − 54/60)g = 0.1g, approximately 0.98 m/s² downward.
Q24. What is the force called by which Earth draws objects toward itself?
[SSC CHSL — 12 Oct 2020, Shift 3]
(A) Air pressure
(B) Thrust
(C) Gravity
(D) Resistance
Answer: (C) Gravity
Explanation: Gravity is the attractive interaction between masses. Earth’s mass produces the force pulling nearby objects toward its centre. In free fall, gravity produces downward acceleration. Air resistance, if present, acts separately and generally opposes the falling motion.
Q23. Which symbol denotes acceleration due to gravity?
[RRB Junior Engineer — 23 May 2019, Shift 3]
(A) Lowercase g
(B) Uppercase G
(C) Greek gamma
(D) Greek epsilon
Answer: (A) Lowercase g
Explanation: Lowercase g represents gravitational acceleration, commonly around 9.8 m/s² near Earth’s surface. Capital G represents the universal gravitation constant, with different units. Confusing the two symbols leads to errors in weight and gravitational-field equations.
Q22. Where on Earth is the acceleration due to gravity generally highest?
[RRB ALP Fitter — 23 Jan 2019, Shift 2]
(A) At the poles
(B) At infinite distance
(C) At the equator
(D) At Earth’s centre
Answer: (A) At the poles
Explanation: Gravity is strongest near the poles because Earth’s radius is smaller there and rotational reduction in effective gravity is minimal. Its value is less at the equator; at the centre, the idealised net gravitational field vanishes.
Q21. If surface gravity is g, what is gravity at height R/2 above Earth’s surface?
[RPSC Senior Teacher Grade II Science — 01 Nov 2018]
(A) 0
(B) 2g/3
(C) 4g/9
(D) g/2
Answer: (C) 4g/9
Explanation: At distance R + h from Earth’s centre, gravity equals GM/(R + h)². With h = R/2, the distance becomes 3R/2. Hence the new g equals GM/(9R²/4) = 4g/9.
Q20. Two equal-density spheres of masses m and 8m fall in the same viscous fluid. If the first terminal speed is v, what is the second?
[RPSC Senior Teacher Grade II Science — 01 Nov 2018]
(A) 0
(B) v
(C) 2v
(D) 4v
Answer: (D) 4v
Explanation: At equal material density, eightfold mass means eightfold volume and twice the radius. Stokes-law terminal speed in a viscous fluid is proportional to radius squared, with other properties fixed. Doubling radius therefore makes terminal speed 4v.
Q19. A dropped stone would take 5 s to hit ground. If stopped after 3 s and released again, how much additional time is needed?
[RPSC Senior Teacher Grade II Mathematics — 29 Oct 2018]
(A) 2 s
(B) 3 s
(C) 4 s
(D) None of these
Answer: (C) 4 s
Explanation: Distance fallen in time t from rest is ½gt². Original total distance corresponds to 25 units of ½g; the first three seconds cover 9 units. Remaining distance is 16 units, so a fresh release takes √16 = 4 s.
Q18. Near Earth, if air friction is negligible, different objects fall with the same what?
[RRB Group D — 09 Oct 2018, Shift 3]
(A) Acceleration
(B) Speed at every starting condition
(C) Velocity under all conditions
(D) Mass
Answer: (A) Acceleration
Explanation: Gravitational force is proportional to an object’s mass, but acceleration equals force divided by that mass. The mass cancels, leaving g. Identically released objects therefore share the same acceleration even if their masses differ greatly.
Q17. Under which condition can a falling object experience gravity alone, without air resistance?
[RRB Group D — 19 Sep 2018, Shift 1]
(A) Underwater
(B) In the atmosphere
(C) In ordinary air
(D) In a vacuum
Answer: (D) In a vacuum
Explanation: A vacuum contains no air to generate drag. A falling body then moves under gravity alone, which is the ideal free-fall condition. In water or air, fluid resistance and possibly buoyancy affect the resulting acceleration.
Q16. Approximately how large is acceleration due to gravity at Earth’s surface?
[RRB ALP CBT-I — 31 Aug 2018, Shift 1]
(A) 9.6 cm/s²
(B) 9.8 m/s²
(C) 10.8 m/s²
(D) 9.8 cm/s²
Answer: (B) 9.8 m/s²
Explanation: The standard near-surface gravitational acceleration is approximately 9.8 metres per second squared. It means a freely falling object’s downward velocity increases by roughly 9.8 metres per second during each second, provided air resistance is negligible.
Q15. The gravitational force acting on a mass m near Earth is equal to which expression?
[SSC CHSL — 17 Mar 2018, Shift 3]
(A) Mass multiplied by gravitational acceleration
(B) Mass divided by gravitational acceleration
(C) Acceleration divided by mass
(D) Reciprocal of mass times acceleration
Answer: (A) Mass multiplied by gravitational acceleration
Explanation: Newton’s second law says F = ma. The force causing free-fall acceleration is the body’s weight, so its magnitude is W = mg. Here m is measured in kilograms and g in m/s², giving newtons.
Q14. A planet has Earth’s mass but twice its radius. How large is its surface gravity relative to Earth’s g?
[SSC CHSL — 15 Mar 2018, Shift 1]
(A) g/4
(B) g/2
(C) 4g
(D) 2g
Answer: (A) g/4
Explanation: Surface gravitational acceleration is GM/R². The mass remains M, but doubling R makes the denominator four times as large. Consequently g′ = GM/(2R)² = g/4. The falling object’s own mass is irrelevant.
Q13. A planet has twice Earth’s mass but the same radius. What is its surface gravity?
[SSC CHSL — 11 Mar 2018, Shift 2]
(A) 2g
(B) g
(C) g/2
(D) 4g
Answer: (A) 2g
Explanation: According to g = GM/R², gravitational acceleration scales directly with planetary mass if the radius is fixed. Replacing M by 2M doubles the acceleration, yielding 2g. This is distinct from doubling the radius, which lowers surface gravity.
Q12. A ball is projected at 40 m/s at 30° to horizontal. With g = 10 m/s², what is its total flight time?
[SSC Scientific Assistant Physics — 25 Nov 2017, Shift 2]
(A) 2 s
(B) 1 s
(C) 4 s
(D) 3 s
Answer: (C) 4 s
Explanation: Time of flight on level ground is T = 2u sinθ/g. Here the initial vertical speed is 40 sin30° = 20 m/s. Thus T = 2 × 20/10 = 4 seconds.
Q11. A cannonball fired at 15° travels 45 m horizontally. For g = 10 m/s², find launch speed.
[SSC Scientific Assistant Physics — 25 Nov 2017, Shift 1]
(A) 20 m/s
(B) 30 m/s
(C) 10 m/s
(D) 40 m/s
Answer: (B) 30 m/s
Explanation: On level ground, range R = u² sin2θ/g. Since sin30° = ½, 45 = u²(½)/10. Therefore u² = 900 and u = 30 m/s, when aerodynamic drag is ignored completely.
Q10. A projectile at 60° reaches maximum height 15 m. If g = 10 m/s², what was launch speed?
[SSC Scientific Assistant Physics — 24 Nov 2017, Shift 1]
(A) 10 m/s
(B) 10√3 m/s
(C) 20 m/s
(D) 20√3 m/s
Answer: (C) 20 m/s
Explanation: The maximum height is H = u²sin²θ/(2g). Substituting H = 15, g = 10 and sin²60° = 3/4 gives 15 = 3u²/80, so u² = 400 and u = 20 m/s.
Q9. A ball launched at 30 m/s, 15° above horizontal, lands at the same level. Take g = 10 m/s². Find range.
[SSC Scientific Assistant Physics — 24 Nov 2017, Shift 2]
(A) 40 m
(B) 50 m
(C) 45 m
(D) 35 m
Answer: (C) 45 m
Explanation: Horizontal range on level ground is R = u²sin2θ/g. Here u² = 900 and sin30° = ½, giving R = 900 × ½/10 = 45 m under ideal projectile assumptions.
Q8. Which expression gives the maximum height of a projectile launched at speed v and angle θ?
[SSC Scientific Assistant Physics — 23 Nov 2017, Shift 2]
(A) v sin²θ/(2g)
(B) v²sin²θ/(2g)
(C) v²sin²θ/g
(D) v sin²θ/g
Answer: (B) v²sin²θ/(2g)
Explanation: At maximum height the vertical component of velocity is zero. The launch vertical speed is v sinθ. Using 0 = (v sinθ)² − 2gH yields H = v²sin²θ/(2g).
Q7. A projectile begins at speed v and elevation angle θ. Which formula gives time to reach greatest height?
[SSC Scientific Assistant Physics — 22 Nov 2017, Shift 2]
(A) v sinθ/g
(B) v²sinθ/g
(C) v²sin²θ/g
(D) v sin²θ/g
Answer: (A) v sinθ/g
Explanation: Vertical velocity changes according to v_y = v sinθ − gt. At maximum height, v_y = 0. Solving gives t = v sinθ/g. The total flight time back to the launch level is twice this time.
Q6. Which quantity remains constant when a ball is thrown vertically upward, neglecting air resistance?
[SSC CGL — 12 Aug 2017, Shift 2]
(A) Total mechanical energy
(B) Displacement
(C) Velocity
(D) Kinetic energy
Answer: (A) Total mechanical energy
Explanation: As the ball rises, kinetic energy decreases while gravitational potential energy increases. The sum of those two energies stays constant if no dissipative force acts. Velocity and displacement change with time, so only total mechanical energy is conserved.
Q5. A ball is projected vertically at 25.2 m/s. When does it reach maximum height? Take g = 9.8 m/s².
[UPSC NDA-II GAT — 18 Sep 2016]
(A) 5.14 s
(B) 3.57 s
(C) 2.57 s
(D) 1.29 s
Answer: (C) 2.57 s
Explanation: The upward velocity decreases by g every second. At the top v = 0, so t = u/g = 25.2/9.8 ≈ 2.57 s. This is the ascent time, not the complete return time.
Q4. One ball rises from ground at 20 m/s; another falls from 40 m at 20 m/s. When and where do they meet? g = 9.8 m/s².
[UPSC NDA-II GAT — 18 Sep 2016]
(A) 3 s; 30.2 m high
(B) 2 s; 20.1 m high
(C) 1 s; 15.1 m high
(D) 5 s; 20 m high
Answer: (C) 1 s; 15.1 m high
Explanation: Both balls have the same downward acceleration, so relative acceleration is zero. Initial closing speed is 40 m/s across a 40 m separation; they meet after 1 s. The rising ball reaches 20 − 4.9 = 15.1 m.
Q3. A body falls from 20 m. After descending 5 m, what portion of its initial gravitational potential energy is lost?
[UPSC NDA-I GAT — 17 Apr 2016]
(A) One-quarter of total energy
(B) One-quarter of initial potential energy
(C) One-quarter of potential energy is gained
(D) Three-quarters of total energy is gained
Answer: (B) One-quarter of initial potential energy
Explanation: The initial potential energy relative to ground is mg × 20. After falling 5 m the height is 15 m, so remaining potential energy is mg × 15. The loss is 5/20, or one-quarter, of the initial value.
Q2. What happens to a ball’s weight when it is carried from Earth’s equator to a pole?
[WBCS Preliminary Examination — 2015]
(A) Its mass increases
(B) Mass and weight both change
(C) Its weight increases
(D) Its weight decreases
Answer: (C) Its weight increases
Explanation: Earth is slightly flattened at the poles and its rotation reduces effective gravity at the equator. The acceleration due to gravity is thus higher at poles. With mass unchanged, weight W = mg increases as the ball moves poleward.
Q1. Why does an artificial Earth satellite remain in orbit instead of falling directly to the surface?
[UPSC Civil Services Preliminary Examination — 2011]
(A) Earth’s attraction vanishes at orbital altitude
(B) The Moon cancels Earth’s attraction
(C) Gravity supplies its steady speed
(D) Earth’s gravity supplies the necessary orbital acceleration
Answer: (D) Earth’s gravity supplies the necessary orbital acceleration
Explanation: Earth’s gravity continuously accelerates the satellite toward Earth and bends its path into an orbit. The satellite also has sufficient tangential speed to keep missing the surface. It is actually in continuous free fall, not beyond gravitational influence.