Question

A trolley of mass m is moving over a smooth surface with velocity v. If a body of certain mass is gently placed on it, its velocity decreases by 25%. The mass of the body placed over the trolley is

Answer 1

Answer:

The mass of the body placed over the trolley is 0.33 kg

Explanation:

Initial mass of the trolley = m kg

Initial velocity = v m/s

When a body of certain mass is gently placed on it, its velocity decreases by 25%.

So final velocity = v - 0.25v = 0.75v m/s

According to law of conservation of momentum,

  Initial momentum = Final momentum

∴ $m\times v=m^{\prime}\times 0.75v$         (Let $m^{\prime}$ be the final mass)

    $m^{\prime}=\frac{1}{0.75}=1\cdot 33m kg$

 Mass of the body placed over the trolley = $m^{\prime}-m=1\cdot 33m-m=0.33kg$