Question

The length of the rod placed inside a rocket is measured as $1m$ by an observer inside the rocket which is at rest. When the rocket moves with a speed of $36\times {10}^{6}km/hr$ the length of the rod as measured by the same observer is :

• A. $0.997m$
• B. $1.003m$
• C. $1m$
• D. $1.006m$

Answer 1

The correct option is C $1m$

When the rocket moves with some velocity, the observer inside it moves with the same speed.

Hence the relative velocity of the rod with respect to the observer remains zero.

Hence he observes the length to be the rest length $=1m$