Question

Two unequal masses are ties together with a cord with a compressed spring in between.
When the cord is burnt with a match releasing the spring, the two masses fly apart with equal
A. (a) Kinetic energy
B. (b) Speed
C. (c) Momentum
D. (d) Acceleration

Answer 1

Correct Answer - C
As `F_(ext)=0`, according to the law of conservation of momentum,
`vecP_1+vecP_2=const ant`.
but initially both the blocks were at rest, so
`vecP_1+vecP_2=0`, i.e., `vecP_2=-vecP_1`
i.e., at any instant, the two blocks will have momentum equal in magnitude but opposite in direction (through they may have different values of momentum at different positions).