- #1

AmagicalFishy

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Hi, folks. Studying for an upcoming Physics exam. I've got a few example problems which the professor has solved—and am getting a different answer, but I don't know where the fault is in my reasoning. Could someone tell me whether or not my answer is, too, correct?

Kinetic Energy at Point A = 0

Potential Energy at Point A = Mgh

Kinetic Energy at Point B = [itex]\frac{1}{2}[/itex]MV

Potential Energy at Point B = 0

Velocity at Point B = [itex]\sqrt{2gh}[/itex]

Work of Friction = μN(C-B) [μ is the frictional coefficient. N is the normal force. C-B is the distance the block travels on the surface with friction]

I came up with this equation, essentially saying

M([itex]\sqrt{2gh}[/itex])

Mgh - μN(C-B) = MV

Mgh - μMg(C-B) = MV

Mg(h-μ)(C-B) = MV

Solve for V

V

----------

The answer my professor gave was: d[itex]\sqrt{k/m}[/itex]

Where

Any help?

## Homework Statement

**Find the speed of the block at point C.**## Homework Equations

Kinetic Energy at Point A = 0

Potential Energy at Point A = Mgh

Kinetic Energy at Point B = [itex]\frac{1}{2}[/itex]MV

_{B}^{2}Potential Energy at Point B = 0

Velocity at Point B = [itex]\sqrt{2gh}[/itex]

Work of Friction = μN(C-B) [μ is the frictional coefficient. N is the normal force. C-B is the distance the block travels on the surface with friction]

## The Attempt at a Solution

I came up with this equation, essentially saying

*the energy of friction from point B to C*taken away from*the kinetic energy of the block at point B*equals the kinetic energy of the block at point C.M([itex]\sqrt{2gh}[/itex])

^{2}[itex]/[/itex]2 - μN(C-B) = MV_{c}^{2}[itex]/[/itex]2 Which simplifies to:Mgh - μN(C-B) = MV

_{c}^{2}[itex]/[/itex]2Mgh - μMg(C-B) = MV

_{c}^{2}[itex]/[/itex]2Mg(h-μ)(C-B) = MV

_{c}^{2}[itex]/[/itex]2Solve for V

_{c}to get:V

_{c}= [itex]\sqrt{2g(h-μ)(C-B)}[/itex]----------

The answer my professor gave was: d[itex]\sqrt{k/m}[/itex]

Where

*d*is the point at which the Block compressed the spring by amount d, and*k*is the spring-coefficient. This answer is much simpler, without a doubt, but I'd like to know if my answer is*wrong*.Any help?

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