- #1

PhizKid

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## Homework Statement

Ball A at rest is dropped from a height H and ball B at the same time is thrown up from the ground. When they collide at height h, the velocity of ball A is twice the velocity of ball B. What is h/H?

## Homework Equations

1D Kinematics

## The Attempt at a Solution

I have no idea which of these equations to use, even when I list all of my knowns and what I can infer from this. I just randomly pick every single equation and try to plug everything in because it all looks about the same to me.

So for ball A:

(Initial velocity) V_0 = 0 m/s

(Final velocity @ collision) V_A = -(2V_B) (negative velocity because it's going downwards)

g = -9.8 m/s^2

(displacement) x - x_0 = h - H

ball B:

(Initial velocity)V_0 = ?

(Final velocity @ collision) V_B = |(V_A)/2| (positive velocity because going upward)

g = -9.8 m/s^2

x - x_0 = h

And t_A = t_B since the same amount of time elapses when they both collide since they were released at the same time.

I tried plugging in for the equations and got all these nonsensical statements that I have no idea what they mean.

I got stuff like V_0 of B = -9.8t but I don't know if that's useful. Also -19.6t = 19.6h + 19.6H and a bunch of other stuff I have no clue if is meaninful or not.