1. OBJECTIVE QUESTIONS
FOR
NEET AIIMS JIPMER

2. PHYSICS THEORY OF RELATIVITY
SET 2 MCQ’S

3. Q1. The kinetic energy of a particle moving with very high speed v is given by (m0= rest mass)

4. ANSWER (D)
EXPLANATION

5. Q2. The apparent length of a metre stick, as measured by an observer at rest when the stick is moving along its length with a velocity 86.6% of velocity of light will be
0.20m
0.35 m
0.50 m
6.5 m

6. ANSWER (C)
EXPLANATION

7. Q3. The speed of an electron accelerated through a potential difference of 1.5 million volt will be
3× m/s
2.9× m/s
2.8× m/s
None of these

8. ANSWER (B)
EXPLANATION

9. Q4. A spaceship moving away from the earth with velocity 0
Q4. A spaceship moving away from the earth with velocity 0.6 c fires a rocket away from earth whose velocity relative to spaceship is 0.6 c. The velocity of the rocket as observed from the earth will be
0.80 c
0.86 c
0.88 c
0.99 c

10. ANSWER (C)
EXPLANATION

11. Q5. At what velocity the kinetic energy of particles is equal to the rest mass energy ?

12. ANSWER (D)
EXPLANATION

13. Q6. An electron is chased by a photon. The speed of the electron is 0
Q6. An electron is chased by a photon. The speed of the electron is 0.9 c. Their relative velocity is C
0.1 c
0.9 c
0.8 c

14. ANSWER (A)
EXPLANATION

15. Q7. A spaceship moving away from the earth with a velocity 0
Q7. A spaceship moving away from the earth with a velocity 0.5 c, firers a rocket towards the earth whose velocity to ship is 0.8 c. The velocity of rocket as observed from earth will be
0.5 c
– 0.5 c
1.0 c
– 1.0 c

16. ANSWER (B)
EXPLANATION

17. Q8. Two space craft A and B are approaching an observer on the moon from two opposite directions with speeds of 0.7 c and 0.6 c respectively. The relative speed of the space crafts as observed by the observers in the two crafts will be nearly equal to
0.90 c
0.92 c
0.82 c
0.80 c0

18. ANSWER (B)
EXPLANATION

19. Q9. A beam of particle of half life 𝟐× 𝟏𝟎 −𝟔 𝒔 travels in the laboratory with speed 0.96 times the speed of light. How much distance does the beam travel before the flux falls to ½ times the critical flux ?
1057 m
2057 m
3057 m
2075 m

20. ANSWER (B)
EXPLANATION
Distance travelled by beam during this time (t) as flux falls to half during this time is
𝑠=0.96𝑐×7.14× 10 −6 =2057 𝑚

21. Q10. At what speed a clock be moved so that it may appear to lose 2 minute in each hour ?
5.5× 10 7 m/s
6.6× 10 7 m/s
7.5× 10 7 m/s
8.8× 10 7 m/s

22. ANSWER (C)
EXPLANATION

23. Q11. A proton is accelerated to a kinetic energy of 𝟏
Q11. A proton is accelerated to a kinetic energy of 𝟏.𝟔𝟎 × 𝟏𝟎 −𝟗 𝑱 in a modern synchotron. If the rest mass of proton is 𝟏.𝟔𝟕 × 𝟏𝟎 −𝟐𝟕 𝒌𝒈, then increase in mass of proton is
0.89× 10 −26 kg
1.78× 10 −26 kg
3.58× 10 −26 kg
3.5× 10 −26 kg

24. ANSWER (B)
EXPLANATION

25. Q12. A rocket ship has to go for its length to be contracted to 99% of its real length by a speed

26. ANSWER (B)
EXPLANATION

27. Q13. A rod stationary relative to the earth is found to be 40 m long by an observer on earth. With what velocity must it move parallel to its length so that its apparent length relative to the observer is reduced to ten metres.
2× 10 8 m/s
2.9× 10 8 m/s
3× 10 8 m/s
2.7× 10 8 m/s

28. ANSWER (B)
EXPLANATION

29. Q14. A particle has an average life about 10-8 s
Q14. A particle has an average life about 10-8 s. How fast must it move increase this average life time by 50% ?
2× 10 8 m/s
2.24× 10 8 m/s
2.48× 10 8 m/s
2.72× 10 8 m/s

30. ANSWER (B)
EXPLANATION

31. Q15. Calculate the ratio of the mass of the electron to its rest mass when it is moving with kinetic energy of 20 MeV. Rest mass of electron = 0.51 MeV. 2
20.1
40.2
10.1

32. ANSWER (C)
EXPLANATION

33. Q16. If 1000 kg of water is heated from 0oC to 100oC, find the increase in the mass of water.

34. ANSWER (B)
EXPLANATION

35. Q17. The total energy generated in a country in a year amounted to 𝟕
Q17. The total energy generated in a country in a year amounted to 𝟕.𝟓 × 𝟏𝟎 𝟏𝟏 𝒌 𝒘𝒉. Find its mass equivalent.
20 kg
25 kg
30 kg
35 kg

36. ANSWER (C)
EXPLANATION