A rod of length 5 m is moving at a speed of 0.6 c. To an observer sitting perpendicular to the direction of motion, the length appears to be?
A.
5 m
B.
4 m
C.
3 m
D.
2 m
Answer: Option A
Explanation:
In Lorentz Length transformation, there is no change in the dimensions of the objects in the direction perpendicular to the direction of motion. Thus, to the observer, the length remains the same.
A 20-year-old person goes at a high speed in a rocket on his birthday. when he comes back to earth after 1 earth year, he would be?
A.
1 year older
B.
2 years older
C.
A few months older
D.
Same age
Answer: Option C
Explanation:
When a person is going around at high speed, time dilation takes place. For that person, the time starts running slowly. Thus, as 1 earth year has passed away but for that person, it must have been only a few months.
The length of a rod seems shorter to an observer when it moves in a specific direction. What change would he observe when the direction of rod changes by 180o?
A.
The rod becomes even smaller
B.
The length of the rod increases
C.
The length of the rod remains the same
D.
The rod has the length equal to its proper length
Answer: Option C
Explanation:
As we know, by Lorentz contraction, l = l0 √1−v2c2. Thus, as it deals with the square of velocity, v, there is no effect on the length of the rod by changing the direction of the rod from v to -v.
An object of length 1 m is moving at speed 0.5c. To an observer at rest relative to the object, the length of the object seems to be?
A.
0.86 m
B.
0.5 m
C.
1 m
D.
0.14 m
Answer: Option C
Explanation:
The observer at rest relative to the object does not notice any kind of contraction of length of the object. It is so because the scale with which he measures will also get contracted by the same amount.
