# Spring and Projectile Motion Problem

1. Nov 24, 2004

### mkcompu

Ok, I need some help getting started with a problem involving a spring and projectile motion.

A picture of the problem is attached.

Part A was easy, done with projectile motion. I worked it out to time = sqrt((-2h)/g).

Now I'm stuck on where to start with part B because we are not given a spring constant. I know that just the speed as it leaves the platform needs to be found because there is no acceleration on the x component.

I played around with simple harmonic motion equations but keep getting stuck on the fact that I dont know what K is or the force needed.

And for reference I'm in ap physics b.

Any help to get me started would be greatly appreciated.

Thanks.

2. Nov 24, 2004

### Staff: Mentor

Hint: You figured out the time in part a. What horizontal distance did it travel in that time?

3. Nov 24, 2004

### mkcompu

Thanks. It was so obvious, I got too caught up in the equations. I never thought I would forget that v=s/t but I just did...Thanks for the reminder.

So I got v=D/sqrt((-2h)/g)

Ok, so then It's a matter of using an equation for velocity of a spring, v=(2piX)/T and combining it with T=2pisqrt(m/k), I can find K [got part D done right there!] and then using w= 1/2kx^2.

Sounds good to me.