Question

Two identical 5 kg blocks are moving with same speed of 2 ms^-1 towards each other along a frictionless horizontal surface. The two blocks collide, stick together and come to rest. Consider the two blocks as a system. Calculate work done by 

(i) external forces and 

(ii) Internal forces.

Answer 1

Here no external forces are acting on the system so

\(\vec F\)_ext = 0 ⇒ W_ext = 0

According to work-energy theorem : 

Total W.D. = Change in K.E.

or W_ext + = Final K.E. – Initial K.E.