Question

A girl of mass $40\text{kg}$ jumps with horizontal velocity $5\text{m/s}$ onto a stationary cart of mass $3\text{kg}$ with frictionless wheels. Find her velocity as the cart starts moving.

• A. $4.65\text{m/s}$
• B. $5.65\text{m/s}$
• C. $6.65\text{m/s}$
• D. $0\text{m/s}$

Answer 1

The correct option is A $4.65\text{m/s}$

From law of conservation of linear momentum,

$m_1{u}_1+m_2{u}_2=(m_1+m_2)v$

$\Rightarrow 40\times 5+3\times 0=(40+3)v$

$\Rightarrow v=4.65\text{m/s}$

Hence, option $\left(A\right)$ is the correct answer.