Calculate Mass Velocity with Energy Methods

[rj101]

Homework Statement

3. A mass m is thrown with a velocity v0 off of a building of height h above the ground. The mass then lands a distance away on a spring (spring constant k) which has an equilibrium length y0 above the ground. If the maximum spring compression is δy = y0 − y, use energy methods to determine the velocity at which the mass was thrown. You can take the other values in the problem to be

h=10m m=1kg, k=29200N/m, y0 =50cm,δy=10cm

You can assume that the mass lands essentially vertically on the spring, and ignore any frictional forces.

Homework Equations

i have no idea how to do this question so i do not know what equations to use

The Attempt at a Solution

i have no idea

Homework Statement

Homework Equations

The Attempt at a Solution

 

[cepheid]

PLEASE SHOW ALL WORK OR LET ME KNOW WHAT EQUATIONS TO USE AND FOR WHAT STEP SO I ALL I HAVE TO DO IS PLUG IN THE NUMBERS thanks!

I'm sorry, but this is against forum rules (you might want to read them more closely). We don't do your homework for you here. That would not help you in the slightest. What are you going to do on an exam if you don't learn any physics and are just spoonfed answers all semester?

Anyway, technically I shouldn't help you at all since you haven't shown any work or made an attempt, but since I'm a nice guy, I will.

I would say that you have to work backwards from the spring compression.

- Applying conservation of energy to the spring, you know that the amount of elastic potential energy stored at max compression must be equal to the initial kinetic energy of the ball upon impact with the spring. Therefore, you know the impact speed.

- From the impact speed, you can figure out from what maximum height the ball must have fallen (it's just free-fall).

- Based on how high above h (the roof), this maximum height is, you can figure out what the vertical launch speed was.

- At this point, I'm not sure how you'd figure out what the horizontal launch speed was, but you could figure it out if you knew the horizontal distance between the spring and the building, because you can figure out the flight time.