Two identical 5 kg blocks approach each other at 2 m/s each on a frictionless horizontal surface. They stick and stop after collision. Treating both as a system, find work done by external force (J).
Physics · Mixed Chapter
JEE Main Practice

Question

Two identical 5 kg blocks approach each other at 2 m/s each on a frictionless horizontal surface. They stick and stop after collision. Treating both as a system, find work done by external force (J).

G1 Physics · Accepted Answer

Step 1: Consider the two blocks together as the system. During collision, inter-block impact forces are internal. Step 2: The surface is frictionless; normal and gravity do no net work along horizontal motion. Step 3: Therefore work done by external forces is 0 J, even though 20 J of kinetic energy converts into internal energy.