Question

A boy of mass 30 kg jumps with a horizontal velocity of 3m * s ^ - 1 onto a stationary cart with frictionless wheels. The mass of the cart is 5 kg. What is his velocity as the cart starts moving? Assume that there is no external unbalanced force working in the horizontal direction

Answer 1

Given:

A boy of mass 30 kg jumps with a horizontal velocity of 3 m/s onto a stationary cart with frictionless wheels. The mass of the cart is 5 kg.

To find:

Velocity of the cart after man jumps?

Calculation:

Since question clearly mentions "no external force" , we can conserve LINEAR MOMENTUM.

Applying Conservation of Linear Momentum:

$\therefore \: (m1)u = (m1 + m2)v$

$\implies \: (30)3 = (30 + 5)v$

$\implies \: 90 = 35v$

$\implies \: v = 2.57 \: m {s}^{ - 1}$

So, velocity of cart-man after man jumps onto cart is 2.57 m/s.