Question 171: Centre of Mass and Rotational Motion

Question

A body of mass 2 kg makes an eleastic collision
with a second body at rest and continues to move
in the original direction but with one fourth of its
original speed. What is the mass of the second
body ?

Accepted Answer

By conservation of linear momentum:
$$2{v_0} = 2\left( {{{{v_0}} \over 4}} \right) + mv \Rightarrow 2{v_0} = {{{v_0}} \over 2} + mv$$
$$ \Rightarrow {{3{v_0}} \over 2} = mv\,\,...(1)$$
Since collision is elastic
$${V_{separation}} = {V_{approch}}$$
$$ \Rightarrow v - {{{v_0}} \over 4} = {v_0} \Rightarrow m = {6 \over 5} = 1.2\,kg$$

Answer

1.2 kg

Answer

1.0 kg

Answer

1.8 kg

Answer

1.5 kg

Centre of Mass and Rotational Motion

A body of mass 2 kg makes an eleastic collision with a second body at rest and continues to move in the original direction but with one fourth of its original speed. What is the mass of the second body ?

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