Question

Consider two observers moving with respect to each other at a speed $v$ along a straight line. They observe a block of mass $m$ moving a distance $l$ on a rough surface. The following quantities will be same as observed by the two observers.

• A. kinetic energy of the block at time $t$.
• B. work done by friction.
• C. total work done on the block.
• D. acceleration of the block.

Answer 1

Answer: (D)

acceleration of the block.

work done and hence kinetic energy depends upon the displacement and velocity of block.
where as acceleration is rate of change of velocity w.r.t. time and both the observers are moving at constant velocity w.r.t each other so acceleration observed will be same.