A person weighing 60 kg moves towards a cart weighing 30 kg and jumps on it.

A person weighing 60 kg moves towards a cart weighing 30 kg and jumps on it. What was the speed of the cart if the speed of the person at the moment of the jump was 2 m / s, and the speed of the cart was 1 m / s?

mh = 60 kg.

mt = 30 kg.

Vch = 2 m / s.

Vt = 1 m / s.

Vт “-?

Let’s write down the law of conservation of momentum.

Before the jump, the total impulse of the person and the cart is: mh * Vh – mt * Vt.

The sign “-” because the speed of the person and the cart are directed in the opposite direction.

Impulse of the person and the cart after the jump: (mh + mt) * Vt “.

mh * Vh – mt * Vt = (mh + mt) * Vt “.

Vt “= (mh * Vh – mt * Vt) / (mh + mt).

VT “= (60 kg * 2 m / s – 30 kg * 1 m / s) / (60 kg + 30 kg) = 1 m / s.

Answer: the trolley speed became Vt “= 1 m / s.