# Homework Help: Momentum/Impulse problems

1. Oct 24, 2004

### DLxX

I need help with this problem.

1) A 0.145kg baseball pitched at 39m/s is hit on a horizontal line drive straight back toward the pitcher at 52m/s. If the contact time between bat and ball is 1.00 X 10^-3s, calculate the average force between the ball and bat during contact.

And for this problem I need to know if the answers I got were correct.

2) A golf ball of mass .045kg is hit off the tee at a speed of 45m/s. The golf club was in contact with the ball for 5.0 X 10^-3s. Find (a) the impulse imparted to the golf ball, and (b) the average force excerted on the ball by the golf club.

This is what I got.

BTW The 5.0 X 10^-3 is my way of showing scientific notion on the computer.
Impulse = 2.03
Average Force = 406

2. Oct 24, 2004

### Leong

Your answers for the second question are correct but if you want to follow the rules of significant figures, round them to 2 significant figures only.
If you can find the average force for the second question, i don't see why you çan't find for the first question.

3. Oct 24, 2004

### DLxX

Well in the first question the ball is pitched to the batter, while in the second question the ball starts of stationary.

4. Oct 24, 2004

### Leong

well, what is the formula you use to find the average force in the second question ?

5. Oct 24, 2004

### DLxX

Fnet = Tri P / Tri T

The Tri being a triange which means P final minus P initial and P meaning Momentum with T meaning Time.

6. Oct 25, 2004

### Leong

$$F_{net}=m*\frac{v-u}{t}$$
v is the final velocity and u is the initial velocity of the baseball. the direction of v is opposite to the direction of u. Insert the appropriate sign after you have choosen your 1-D reference frame.