# Projectile and SHM

1. Mar 9, 2006

### kentus

Hey
i came across this physics problem in a uni textbook however i am stuck,

Q: A 70.0kg circus performer is fired from a cannon that is elevated at an angle of 40.0' (degrees) above the horizontal. The cannon uses strong elastic bands to propel the performer, much in the same way that a slingshot fires a stone. Setting up fro this stunt involves stretching the bands by 3.00m from the unstrained length. At the point where the performer flies free of the bands, his height above the foor is the same as that of the net into which he is shot. He takes 2.14s to travel the horizontal distance of 26.8m between this point and the net. Ignore friction and air resistance and determine the effective spring constant of the firing mechanism.

I understand that the horizontal speed is equal to (26.8/2.14) = 12.52m/s and that their is stored energy into the bands?

thanks

2. Mar 9, 2006

### Harmony

This is the way I approach the question.
1. Determine the initial velocity.
2. Find the kinetic energy.
3. Use the formula E=0.5kx^2

3. Mar 10, 2006

### kentus

does all the EPE get transferred to KE?

4. Mar 10, 2006

### Harmony

I suppose so. Please correct me if I am wrong.

Last edited: Mar 10, 2006
5. Mar 10, 2006

### lightgrav

You're supposed to ignore friction ... ignore INTERNAL friction, too.

Make sure you include the *vertical* component of velocity also!

6. Mar 12, 2006

### kentus

yep alright thanks for the help guys !