Physics 11 Help

[rahul_rudani]

hey guys,

i couldn't figure out this question. Can anyone help me do this question.

 

- 2 persons are skiing down the frictionless hill. The height of the hill is 12m. Calculate the velocity (m/s) at the end of the hill (assume the initial velocity is 0m/s)

 

- I think it has something to do with Kinetic Energy. But, i don't know where to start from. I need the answer for Monday. So, if anyone can solve this problem, I would be thankful.

[fafalone]

I don't think you can solve that without some more information (the slope of the hill).

[rahul_rudani]

maybe mass would help. Let's assume that the mass of the person is 50 kg. But, our teacher didn't even give us the mass to solve the problem.

[fafalone]

You really need to have the angle to solve this problem.

[Guest Meninger]

Rudani,

 

You can solve this using the concept of kinetic energy.

 

Remember change in KE = the change in potential energy.

 

You do not need to have the angle since potential energy is a non-conservative force (I think).

 

The change in potential energy would simply be

9.8m/s^2 X mass X (the change in height).

 

By the time the skier gets to the bottom of the hill, the magnitude of the potential energy that I have shown above will be converted to kinetic energy.

 

So since the change in KE will be equal to KE (final) - KE (initial)

and since the initial KE is zero, since velocity is zero we can say that

 

9.8m/s^2 X mass X (the change in height) = X (velocity squared)

 

You see that mass is on both sides, you can cancel them out

 

9.8m/s^2 X (the change in height) = (velocity squared)

 

Solve for velocity

 

You need anymore help with any other hw problems go to

http://www.physicsforums.com and go to homework help section.

[rahul_rudani]

Thank you very much Meninger.

I got the idea of how to solve the problem.