Question

On a frictionless surface. An 80kg person was with a 50kg person at rest. After they pushed each other, B moved at 8.0 m/s to the right. Whar is the velocity of A ? If A = 80 kg and B = 50 kg

Answer 1

Given:

The mass of the person A is

$m_A=\text{ 80 kg}$

The mass of the person B is

$m_B\text{ = 50 kg}$

The initial velocity of A and B is zero as it is at rest.

The final velocity of person B is

$v_B=\text{ 8 m/s }$

towards right.

To find the velocity of A.

Explanation:

According to the conservation of momentum, the final velocity of person A will be

$\begin{gathered} m_A\times0+m_B\times0=m_Av_A+m_Bv_B \\ v_B=-\frac{m_Bv_B}{m_A} \end{gathered}$

On substituting the values, the final velocity of person A will be

$\begin{gathered} v_B=-\frac{50\times8}{80} \\ =-5\text{ m/s} \end{gathered}$

Here, the negative sign indicates that the final velocity i