# Homework Help: Physics 11, kinetic energy problem

1. Dec 20, 2006

### Iceclover

Hey if anyone could help me work through a couple of problems that would be great!

1. The problem statement, all variables and given/known data

It is not uncommon during the service of a professional tennis player for the racquet to exert an everage force of 150.0N on the ball. If the ball has a mass of 0.060kg and is in contact with the strings of the racquet for 0.030s what is the kinetic energy of the ball as it leaves the racquet? Assume the ball starts from rest

2. Relevant equations

Ek=1/2mv^2

3. The attempt at a solution
I'm not sure really where to start here....

2. Dec 20, 2006

### radou

A hint: impulse.

3. Dec 20, 2006

### mbrmbrg

Well, you know what you'll need to find Kinetic Energy--mass and velocity. You're given mass. Can you think of any other equations that might help you find velocity?

4. Dec 20, 2006

### Iceclover

what do i do once i've figured that out?

5. Dec 20, 2006

### Iceclover

d=vt but i don't have a distance either

6. Dec 20, 2006

### mbrmbrg

Once you've figured what out?

7. Dec 20, 2006

### Iceclover

oh my god i think i got it, will someone let me know if i got it right, just let me work it out.

8. Dec 20, 2006

### radou

There is no need to create so many posts.

9. Dec 20, 2006

### Iceclover

i got 169J

10. Dec 20, 2006

### mbrmbrg

Looks OK to me, whose brain is fried!

Last edited: Dec 20, 2006
11. Dec 20, 2006

### cristo

Staff Emeritus
That's correct.

12. Dec 20, 2006

### Iceclover

p=Ft
p=150(0.030)
p=4.5

p=mv
4.5=(0.06)(v)
v=75m/s

Ek=1/2m^2
Ek=1/2(0.060)(75^2)
Ek=169J

13. Dec 20, 2006

### Iceclover

Ok i have a couple of other question so if anyone wants to stick around and help...?

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