Question

An 80.0 kg man playing hockey catches a puck moving at 20.0 m/s. The man is initially at rest. The man and puck move together after the collision. The puck's mass is 0.17 kg. What is the final velocity?

Answer 1

using conservation of momentum, the initial momentum of the man is 0, and the puck's is 0.17kg*20m/s=3.4 kg*m/s.  The final mass is 80.17kg.  The final momentum is still p=mv=3.4kg*m/s, so v=3.4/80.17= 0.0424m/s

Answer 2

`V_s`=0.0424m/s

Step-by-step explanation:

Using the law of the conservation of linear momentum P:

`P_i = P_f`

so:

`M_mV_(mi)+M_pV_(pi) = M_sV_s`

where
`M_m` is the mass of the man,
`V_(mi)` is the initial velocity of the man,
`M_p` is the mass of the puck,
`V_(pi)` is the initial velocity of the puck,
`M_s` is the mass of the puck and the man and
`V_s` is the velocity of both after the collition.

Replacing values, we get:

`(80kg)(0m/s)+(0.17kg)(20m/s) = (80kg + 0.17kg)V_s`

Finally, solving for
`V_s`:

`V_s`=0.0424m/s