A roller-coaster car starts at a height of 90 m at Point A and is moving at a speed of 20 m/s on a later hill at Point C. Assuming friction does not affect the motion of the car, what is its height at Point C?

Question

anonymous · Answer

Here is the first one @wolfe8 :)

wolfe8 · Answer

So energy is conserved. So at C, it will have kinetic energy and potential energy totaling to the potential energy at A. Can you set up the equations?

anonymous · Answer

I think so! One sec...

anonymous · Answer

Is this an instance where we are trying to find deltaK?

anonymous · Answer

Or is it just K = 1/2 m * v^2?

wolfe8 · Answer

That is the kinetic energy. That plus the potential energy mgh at C will give you mgh at A

anonymous · Answer

OH okay, so it's 1/2 *m * v^2 + mgh = PE at A

anonymous · Answer

But they don't give me m :/

wolfe8 · Answer

Yup! And PE=mgh. To make it not too confusing, you can write it this way:
$$mgh _{A}=\frac{ 1 }{ 2 }mv ^{2}+mgh _{C}$$

wolfe8 · Answer

And since m is present on every term in the equation, you can cancel it out :)

anonymous · Answer

OH Cool!

So..

9.8 * 90 = 1/2 * 20 ^2 + 9.8 * hc

anonymous · Answer

That was easy! Great :)! Thanks.  I'll start the new one

wolfe8 · Answer

Yup!

directrix · Answer

@Daniellelovee