# Supposed Energy ProblemsHelp

1. Oct 4, 2004

### Spitting_Camel

Supposed Energy Problems..Help!!

I have 2 questions...

A projectile is launched with a speed of 40 m/s at at angle of 60 degrees about the horizontal. Find the maximum height reached by the projectile during its flight by using conservation of energy.

I guess I don't get how to get the answer from a bunch of work, PE and KE equations. If you could give me a hint on this one on where to start, what equations to use I can probably figure it out.
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Second question...

A bead of mass m=5.00kg is released from point A and slides on the frictionless track shown in figure P5.30. Determine (a) the bead's speed at points B and C and (b) the net work done by the force of gravity in moving the bead from A to C.

I am also completely lost on this question too. I don't understand how you can get speed (v) from any of the work, PE, KE equations. Please give me a hint! I attached a crude picture of the graphic for this one...

Thank you so much if you respond.

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2. Oct 4, 2004

### stunner5000pt

first question

dK + dU = 0

KE ( final) - KE ( initial) + PE ( final) - PE (initial) = 0

what is the velocity of the ball when it reaches th highest point? Who cares about angles, talk about vertical speed, if the ball were throw staright up, woul it make a difference? I know you've been shown this in class

What is the initial velocity? Find the VERTICAL velocity of the ball using the angle that you are given

What is the initial height? Was it shot from the ground or from a height? in that case waht is vakue of initial height?

What is final height? given all these clues can you figure it out?