- #1

Ering

- 8

- 0

## Homework Statement

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*Ally starts at rest with a height H above the ground and slides down a frictionless slide. The bottom of the slide is a height h above the ground. Ally then leaves the slide horizontally, striking the ground a distance d from the end of the slide (where she left the slide).*

Use energy methods to help determine the initial height H of Ally in terms of h and d.

Use energy methods to help determine the initial height H of Ally in terms of h and d.

## Homework Equations

Ei = Ef (initial energy equals final energy)

Ki + Ui = Kf + Uf (initial kinetic energy plus initial gravitational potential energy equals final ...)

--> 1/2 m(vi)^2 + mg(yi) = 1/2 m(vf)^2 + mg(yf)

m = mass

g = gravity

y = height

v = initial/final velocity

## The Attempt at a Solution

I started by writing out:

Ki + Ui = Kf + Uf

Then, i figured since Ally starts at rest, the initial velocity is zero which would cancel out Ki. And since Ally lands on the ground, the final height (yf) would be zero so i canceled the grav. potential final energy too.

So,

mg(yi) = 1/2 m(vf)^2

Since I want the initial height (yi), i rearranged the equation to solve for yi, and canceled m's

yi = vf^2 / 2g

Then i figured I could substitute some equation in for vf^2 that incorporated the h and d... however I'm not sure which equation(s) i could use?

Probably something to do with projectile motion, but I'm really not sure where to go from here. Thanks for any help

-stuck and stressed