# Homework Help: Impulse help!(3 problems)

1. Oct 21, 2007

### crimsonfears

Okay, I was absent the day we did impulse at school, so now I'm confused as to how to do some of it. I just need to know how to set up the problems, I know that impulse=F$$\Delta$$t and that F$$\Delta$$t=m$$\Delta$$v...but I don't know where to go after that.

The first problem:
Two children, totaling 200 kg, are traveling at 10 m/sec in a 100-kg bumper car during an amusement park ride. They deliberately collide with an empty second car, mass 100 kg, which is at rest. Afterwards, the car with the two children moves off at a speed of 4.0 m/sec. What is the final velocity of the empty car?

The Second problem:
James, a 65-kg skin diver, shoots a 2.0-kg spear with a speed of 15 m/sec at a fish which is darting past him. How fast does James recoil when the spear is initially released?

The Third problem:
On a hot summer day, Jack and Leon are fishing in their boat, when they decide to jump into the water to cool off. Jack, 45-kg, jumps off the front of the boat with a speed of 2 m/sec. While at the exact same moment, Leon, 90-kg, jumps out of the back of the boat at a speed of 4 m/sec. If the boat has a mass of 100 kg and was at rest prior to the two boys jumping off, what will be its velocity just after both boys have abandoned ship?

2. Sep 23, 2008

to the find final velocity of empty cart....
in the equation....let P the momentum
P(initial)=P(final)
MV1+ MV2 = MV1 + MV2
300kg(10m/s)+0=300kg(4.0m/s)+100kgV2
3000kg*m/s-4800kg*m/s=100kgV2
20400kg*m/s=100kgV2
----------------------(divided by 100kg)
100kg
V2=204m/s(final velocity of the empty cart)

3. Sep 23, 2008