Question

Two identical blocks each of mass 10 kg are moving with a speed of 4m/s 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, work done by external force is

• A. Zero
• B. 160 J
• C. 80 J
• D. 40 J

Answer 1

The correct option is A

Zero

The net external force acting on the system is zero hence the work done by external forces is zero. Here the loss in kinetic energy is due to the internal forces between the blocks during collision