Question

A heavy particle moving with 5m/sec suffers on elastic collision with a light particle at rest
after collision, the velocity of light particle will be
a. 5m/sec
b. 10m/sec c. 20m/sec
e. NOT
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Answer 1

A heavy particle moving with 5m/sec suffers on elastic collision with a light particle at rest.

after collision, the velocity of light particle will be..

Coefficient of restitution :

It is the ratio of velocity of separation to the velocity of approach. it is generally denoted by e.

• for elastic collision, e = 1
• for inelastic collision, 0 < e < 1
• for perfectly elastic collision, e = 0

here mentioned that collision between heavy and light particles were elastic.

∴ velocity of separation = velocity of approach [ ∵ e = 1 ]

⇒$\bf v_{heavy}-v_{light}=u_{light}-u_{heavy}$

here, $\bf u_{heavy}=v_{heavy}=5m/s$

velocity of heavy particle remains unchanged because particle does strike have enough momentum to change its direction or magnitude.

$\bf\text{also},u_{light}=0$

⇒5m/s - $\bf v_{light}=0-5m/s$

⇒$\bf v_{light}=10m/s$

Therefore the velocity of light particle will be 10 m/s. hence option (b) is correct choice.