Question

What is the momentum of these two sea creatures just after their collision?

A 1000-kg whale swims horizontally to the right at a speed of 6.0 m/s. It suddenly collides directly with a stationary seal of mass 200 kg. The seal grabs onto the whale and holds fast. You can neglect any drag effects of the water during the collision.

Answer 1

The final momentum is `6000 (kg*m)/s`

Explanation:

The momentum is conserved.

`"Total momentum before", P_(ti) = "total momentum after", P_(tf)`

`P_(ti) = M*u_1 + m*u_2 = (M+m)*v = P_(tf)`

`P_(ti) = 1000 kg*6.0 m/s + 200 kg*0 = P_(tf)`

`6000 kg*m/s + 0 = 1200 kg*V = P_(tf)`

`P_(tf) = 6000 (kg*m)/s`

We could use this line, `6000 kg*m/s + 0 = 1200 kg*V = P_(tf)`, to solve for V, the velocity of the whale/seal combination. But the question does not ask for that. So just calculating the initial momentum gives us the final momentum -- because they must be equal.

I hope this helps,
Steve