Question

A 0.450-kg ice puck, moving east with a speed of 5.16 m/s , has a head-on collision with a 0.950-kg puck initially at rest. Assume that the collision is perfectly elastic.

What is the speed of the 0.450-kg puck after the collision?

Express your answer to three significant figures and include the appropriate units.

What is the speed of the 0.950-kg puck after the collision?

Express your answer to three significant figures and include the appropriate units.

Answer 1

Given, the first ice puck has mass (m) = 0.450 kg

the first ice puck has initial velocity (u₁) = 5.16 m/s

the first ice puck has mass (M) = 0.950 kg

the first ice puck has initial velocity (u₂) = 0 m/s

Let the final velocity of mass mafter collision is v₁ and final velocity of mass M after collision is v₂ .

Now from conservation of momentum ,

  

or,

or,   

or, ..........................(1)

Here the collision is perfectly elastic. So, in this case coefficient of restitution (e) will be 1.

The coefficient of restitution is defined as   

for this case

e = 1

or,   

uu2

or,

or,

or,

putting this value in equation (1), we get

  

or,   

or,   

or,

1.4v1- -2.58

or,   

So,

Hence, the speed of the 0.450 kg puck after collision is 1.84 m/s in the opposite direction of initial motion (i.e in west direction) and the speed of 0.950 kg puck after collision is 3.32 m/s in the east direction .

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