Answer to Question #97816 in Mechanics | Relativity for C

Question

In a work energy thereom question,they can say calculate the distance up the ramp while only giving us the frictional force and the velocities .I saw the solution,to find the distance they use the formula Wnet=Ek But then Wnet should also consist of applied force,gravitational force parallel and frictional force.In this case they only used the frictional force as it was the only information given and left out applied force.Does this mean that we must keep a sum simple and not try to find out applied force if its not given?and only work with information that is given?So under Wnet,there is only friction,is that possible?

Answer 1

No,It does not mean that we must keep the sum simple and left out other forces .reason behind not using other forces is that only frictional force is working in the given situation.

In this case,

$W_{net}=Friction=E_k$

because only friction force is working for stopping the ramp and all the kinetic energy will be lost in the form of frictional force and all the work is done by friction for stopping it.