A 4 kg block ‘A’ and a 3 kg block ‘B’ are pushed together against a spring ...

A 4 kg block ‘A’ and a 3 kg block ‘B’ are pushed together against a spring, and are tied with a cord. When cord breaks, the 3 kg block moves to the right at 18 km/s. What is the velocity of the 4 kg block?

Solution

The velocity of each block can be found using the law of conservation of momentum. Before the cord breaks, the momentum of the two blocks is equal and opposite. After the cord breaks, the momentum of the two blocks is conserved, meaning that the sum of their momenta remains constant.

The momentum of block A is 4 kg * velocity of block A. The momentum of block B is 3 kg * 18 km/s. Setting the sum of the two momenta equal to the initial total momentum, we have:

4 kg * velocity of block A + 3 kg * 18 km/s = 3 kg * 18 km/s + 4 kg * velocity of block A

Solving for the velocity of block A:

velocity of block A = 18 km/s * 3 kg / (3 kg + 4 kg) = 13.5 km/s.

So, the velocity of the 4 kg block is 13.5 km/s.

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