How to find work done by friction?

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To find the work done by friction as a ball rolls down a ramp, one can use the equation for work done by non-conservative forces, which equals the change in energy. The challenge lies in determining the force of friction without knowing the coefficient of friction. By calculating the energy at the top and bottom of the ramp, one can identify the energy lost, which is attributed to friction. Ultimately, while the exact force of friction is unknown, the work done by friction can still be inferred from the energy loss during the ball's descent. Understanding this relationship is key to solving the problem effectively.
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Homework Statement


"In more than one way, find the loss of energy of the ball as it rolls down the ramp."

If for one method, I use WNon-conservative force = Change in Energy, would the work be by kinetic friction?

If it is, then how would I find the work done by friction (which is the NCF) if I only have the following information:
http://i1097.photobucket.com/albums/g349/Physics_/Energy.jpg
Mass of ball = 0.0083 kg


Homework Equations


Uk = Ffriction/ Normal
WNCF = Change in energy
N = mg

The Attempt at a Solution


This is where I got stuck - I tried to find Ffriction but I don't have Uk.
 
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you don't need to know the coefficient of friction. you just need to know how much work is done by the friction.

If you calculate the energy on top of the ramp and at the bottom, you will realize that some of the energy is gone. Where did it go to?
 
kudoushinichi88 said:
you don't need to know the coefficient of friction. you just need to know how much work is done by the friction.

If you calculate the energy on top of the ramp and at the bottom, you will realize that some of the energy is gone. Where did it go to?

But if Wfriction = Ffriction (x) and I don't know the force of friction, how do I find it's work?

And it goes to friction, doesn't it? :O
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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