# Homework Help: SImple Harmonic Motion

1. Mar 9, 2006

### kbean5588

These questions on my hw are so hard. anyone get them?

"The Spring constant for the spring in a special cannon is 1800N/m. In cocking the cannon, the spring is compressed .55m. What is the initial speed of a 7.0 kg cannonball at rest on the free end of the spring when it is released?"

"I went bugee jumping and I was standing on a platform that is 46.0m high. My mass is 68.0kg and my bungee cord is 9.00 m long (unstretched). The cord behaves like an ideal spring and has a constant of k=66.0N/m. I fall off the platform from rest and I want you to tell me my velocity when I am (a) 37 m off the ground and (b) 15 m off the ground."

2. Mar 9, 2006

### topsquark

I am assuming your cannon is horizontal rather than pointing up. Use the Work-Energy Theorem. You can find the initial spring PE. You can use that to predict the final KE.

-Dan

3. Mar 9, 2006

### topsquark

You can find how fast the jumper is moving when the bungee cord is extended, but not stretched. (That's the 37 m reading). For the 15 m reading, you know how far the bungee cord is stretched, so you can find the PE due to that. You also know the gravitational PE. From these you can find the KE.

-Dan