Physics Problem. Please help.?

Question

A block starts from rest at a height of 5 m on a fixed inclined plane. The acceleration of gravity is 9.8. What is the speed of the block at the bottom of the ramp? Answer in units of m/s.
Data:
The angle of inclination of the plane is 25 degrees and the coefficient of sliding friction between the plane and the block is 0.1. The mass of the block is 4.8 kg.

Please give me the process.

Answer 1

The way to approach this is energy conversion. The potential energy of the block at the top of the ramp is m*g*h. This is converted to kinetic energy at the bottom = .5*m*v^2 and friction heat loss of Fr*L, where Fr is the force of friction and L = length of the ramp = h/sin(A). (Constant friction force times distance = work done against friction = energy lost to friction), Friction is the component of weight normal to the plane times the coefficient of friction. The normal component is fn = mg*cos(A) so the frictional force is then Fr= mg*K*cos(A), where K=coeff of friction

Thus the energy balance equation is

.5m*v*2 = m*g*h - m*g*h*K*cos(A)/sin(A)]

v = sqrt{2*g*h*[1 - K*cot(A)]}

You can put the numbers in for g, h, K, and A. Note that the mass doesn't matter.

EDITED

While the above method is simplest, the problem can also be solved using f=ma, finding the forces and accelerations. I have prepared a solution using "Word Equation" which shows both methods in clearer notation. If you are interested, find it at
http://img167.imageshack.us/img167/2505/rampvelocityug2.png

Answer 2

I know absolutely nothing about physics, but I asked a friend of mine...and this is what he gave me...

Fn = cos(A) * Fp ... Fp = sin(A) * Fg ...
9.8 * 4.8 * sin(25) = Force down
0.1 * cos(25) * 4.8 * 9.8 = Force friction
9.8 * 4.8 * sin(25) - 0.1 * cos(25) * 4.8 * 9.8 = F

put it in your calc
make sure you're in degrees

9.8 * sin(25) - 0.1 * cos(25) * 9.8 = a...
5 / sin(25) = d...

so

10 / sin(25) * 9.8 * sin(25) - 0.1 * cos(25) * 9.8
^_^ that's the answer, whatever that gives

I hope that helps and I hope you can figure it out from there...heh...