Question

i) State the law of conservation of momentum. (ii) A body of mass 5 kg, initially moving with a velocity of 20 m/s, collides with another body of mass 25 kg at rest. After collision velocity of first body becomes 10 m/s. Find the velocity of the second body.

pls help!!!

Answer 1

(i)

The Law of Conversation of Momentum states that for a collision occurring between object 1 and object 2 in a system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision.

(ii)

mass 1 = $m_{1}$ = 5 kg

initial velocity 1 = $u_{1}$ = 20 m/s

mass 2 = $m_{2}$ = 25 kg

initial velocity 2 = $u_{2}$ = 0 m/s

final velocity 1 = $v_{1}$ = 10 m/s

final velocity 2 = $v_{2}$

so, by Law of conversation of momentum:

$p_{i}$ = $p_{f}$ {where p = momentum) (i = initial, f = final)

so,

$m_{1} * u_{1}$ + $m_{2} * u_{2}$

=

$m_{1} * v_{1}$ + $m_{2} * v_{2}$

∴, by substituting values:

5 * 20 + 25*0 = 5*10 + 25* $v_{2}$

100 = 50 + 25 * $v_{2}$

$\frac{50}{25}$ = $v_{2}$

2 m/s = $v_{2}$

∴ Thus, the second objects final velocity is 2 m/s