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Homework Help: Spring and Projectile Motion Problem

  1. Nov 24, 2004 #1
    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.

  2. jcsd
  3. Nov 24, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: You figured out the time in part a. What horizontal distance did it travel in that time?
  4. Nov 24, 2004 #3

    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.
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