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Special Relativity MCQs — Physics

90 multiple-choice questions on Special Relativity from Physics, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. Two inertial frames move relative to each other with:

  1. constant velocity
  2. increasing speed
  3. constant acceleration
  4. circular motion

Answer: A) constant velocity

Explanation: Neither accelerates. SLO P-11-F-01 · Understanding

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2. Muons created in the upper atmosphere reach the ground, though their half-life is very short, because of:

  1. mass decrease
  2. time dilation
  3. the Doppler effect
  4. length expansion

Answer: B) time dilation

Explanation: Their clocks run slow for us. SLO P-11-F-05 · Understanding

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3. The headlights of a car moving at speed v emit light that travels (relative to the road) at:

  1. c
  2. v
  3. c + v
  4. c - v

Answer: A) c

Explanation: Independent of source speed. SLO P-11-F-02 · Understanding

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4. A merry-go-round is a non-inertial frame because it is:

  1. moving at constant velocity
  2. at rest
  3. rotating (accelerating centripetally)
  4. very large

Answer: C) rotating (accelerating centripetally)

Explanation: Direction of velocity keeps changing. SLO P-11-F-01 · Understanding

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5. The idea of space-time was developed by:

  1. Hermann Minkowski, building on Einstein's work
  2. Michael Faraday
  3. Galileo
  4. Isaac Newton

Answer: A) Hermann Minkowski, building on Einstein's work

Explanation: Minkowski space-time (1908). SLO P-11-F-06 · Knowledge

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6. A spaceship moving at 0.5c shines a light forward. An observer on Earth measures the light's speed as:

  1. 1.5c
  2. c
  3. 2c
  4. 0.5c

Answer: B) c

Explanation: Light speed is invariant. SLO P-11-F-02 · Understanding

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7. The two postulates together lead to:

  1. time dilation and length contraction
  2. absolute time
  3. infinite speeds
  4. constant mass at all speeds only

Answer: A) time dilation and length contraction

Explanation: Consequences of special relativity. SLO P-11-F-04 · Knowledge

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8. In a non-inertial frame, observers need to introduce:

  1. fictitious (pseudo) forces such as centrifugal force
  2. gravitational waves
  3. no extra forces
  4. magnetic fields

Answer: A) fictitious (pseudo) forces such as centrifugal force

Explanation: To explain apparent accelerations. SLO P-11-F-01 · Understanding

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9. A rod of proper length 100 m moves at 0.6c along its length. An observer at rest measures its length as:

  1. 160 m
  2. 80 m
  3. 800 m
  4. 40 m

Answer: B) 80 m

Explanation: L = L0 1 - v^2/c^2 = 100 1 - 0.6^2 = 80 m. SLO P-11-F-05 · Understanding

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10. Einstein's postulates imply that simultaneity is:

  1. always the same for all observers
  2. relative
  3. impossible
  4. absolute

Answer: B) relative

Explanation: Different observers may disagree. SLO P-11-F-04 · Knowledge

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11. A clock in a spaceship moving at 0.99c records 1 s (proper time). An Earth observer measures the interval as:

  1. 3.54 s
  2. 14.2 s
  3. 7.09 s
  4. 70.9 s

Answer: C) 7.09 s

Explanation: t = gamma t0 = 1 1 - 0.99^2 = 7.09 s. SLO P-11-F-05 · Understanding

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12. When space-time bends and ripples, it can cause:

  1. objects to become charged
  2. objects to change colour
  3. stretching and compression of objects, as when gravitational waves pass
  4. no effects

Answer: C) stretching and compression of objects, as when gravitational waves pass

Explanation: As in the SLO. SLO P-11-F-06 · Knowledge

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13. Treating time as the fourth dimension means that motion through space affects:

  1. the colour of objects
  2. electric charge
  3. nothing
  4. the passage of time

Answer: D) the passage of time

Explanation: Linked in relativity. SLO P-11-F-06 · Knowledge

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14. The constancy of c is the basis for defining the:

  1. kilogram
  2. ampere
  3. metre (the distance light travels in 1299,792,458 s)
  4. kelvin

Answer: C) metre (the distance light travels in 1299,792,458 s)

Explanation: SI definition. SLO P-11-F-02 · Understanding

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15. From the muon's point of view, it reaches the ground because:

  1. the atmosphere is length-contracted
  2. its half-life increases in its own frame
  3. gravity pulls it
  4. it travels faster than light

Answer: A) the atmosphere is length-contracted

Explanation: Equivalent explanation. SLO P-11-F-05 · Understanding

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16. Which statement follows from the constancy of c?

  1. Light can be stopped
  2. Two observers in relative motion can disagree about time intervals
  3. Lengths are absolute
  4. All clocks tick at the same rate

Answer: B) Two observers in relative motion can disagree about time intervals

Explanation: Time dilation. SLO P-11-F-02 · Understanding

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17. At v = 0.6c, the Lorentz factor is:

  1. 1.6
  2. 1.25
  3. 0.6
  4. 0.8

Answer: B) 1.25

Explanation: 1 - 0.36 = 0.8; gamma = 1/0.8. SLO P-11-F-03 · Understanding

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18. An inertial frame of reference is one that:

  1. is always at rest relative to the Sun
  2. is not accelerating (at rest or moving with constant velocity)
  3. is accelerating
  4. is rotating

Answer: B) is not accelerating (at rest or moving with constant velocity)

Explanation: Newton's first law holds in it. SLO P-11-F-01 · Understanding

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19. The second postulate of special relativity states that:

  1. nothing moves faster than sound
  2. energy is conserved
  3. the speed of light in a vacuum is the same for all inertial observers
  4. space is absolute

Answer: C) the speed of light in a vacuum is the same for all inertial observers

Explanation: Constancy of c. SLO P-11-F-04 · Knowledge

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20. Einstein's assumption about light removed the need for:

  1. atoms
  2. electromagnetic waves
  3. gravity
  4. the 'luminiferous aether'

Answer: D) the 'luminiferous aether'

Explanation: No absolute frame. SLO P-11-F-02 · Understanding

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21. The Michelson–Morley experiment found:

  1. no change in the speed of light due to the Earth's motion
  2. that light slows down in the direction of motion
  3. the 'aether'
  4. that light is infinitely fast

Answer: A) no change in the speed of light due to the Earth's motion

Explanation: Supports Einstein's postulate. SLO P-11-F-02 · Understanding

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22. The laws of physics take the same simple form in all:

  1. rotating frames
  2. accelerating lifts
  3. non-inertial frames
  4. inertial frames

Answer: D) inertial frames

Explanation: Basis of special relativity. SLO P-11-F-01 · Understanding

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23. Space-time is a mathematical model in which:

  1. time is removed
  2. only one dimension exists
  3. time is treated as a fourth dimension together with three dimensions of space
  4. space has four dimensions and time none

Answer: C) time is treated as a fourth dimension together with three dimensions of space

Explanation: Four-dimensional continuum. SLO P-11-F-06 · Knowledge

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24. The 'universal speed limit' means that information:

  1. has no speed
  2. travels instantly
  3. cannot travel faster than light
  4. travels at the speed of sound

Answer: C) cannot travel faster than light

Explanation: Causality. SLO P-11-F-02 · Understanding

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25. Which is NOT relative in special relativity?

  1. lengths
  2. simultaneity
  3. time intervals
  4. the speed of light in a vacuum

Answer: D) the speed of light in a vacuum

Explanation: Invariant. SLO P-11-F-03 · Understanding

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