# Physics-bobpursleyplease check

posted by
**Joey** on
.

This is the question I posted about two hours ago and I worked it out two ways-could you scroll down and check it, please?If I have a roller coaster, and hill 1 height is 50cm and hill height 2 is 25 cm and the PE is .9 as it approaches the top of hill 2, how do I calculate the speed.

Please help

Physics-Please help - bobpursley, Thursday, November 4, 2010 at 5:52pm

THe PE is .9 where? Where did the coaster start?

Physics-Please help - Joey, Thursday, November 4, 2010 at 5:54pm

The coaster started at .18PE-the .9 is the PE at the top of the second hill.The second hill is lower.

Physics-Please help - bobpursley, Thursday, November 4, 2010 at 6:01pm

Well, the difference in the two Potential energies is now KEnergy, 1/2 mv^2, solve for v.

Physics-Please check - Joey, Thursday, November 4, 2010 at 6:21pm

. The way to calculate this is you take the KE would be .9. You would say .9 = ½ (.035 x v^2) = 2.215. Correct or no?

Physics-Please check - Joey, Thursday, November 4, 2010 at 7:31pm

Should I have done this as 1/2mv^2 = mgh

Cross out like terms and get to v^2 = square root of 2 x g x .25m(h)= 2.125 m/s

Would this be correct?