# Conceptual question; cylinder moving up an inclined plane

• konichiwa2x
In summary, the frictional force between the cylinder and the incline opposes the cylinder's motion, causing it to roll up the incline.
konichiwa2x
A cylinder rolls up an inclined plane, reaches some height and rolls down (withot slipping throughout these motions). The directions of frictional force acting on the cylinder are : (more than one option may be correct)

(a) Up the incline while ascending and down the incline while descending.
(b) Up the incline while ascending as well as descending.
(c) Down the incline while ascending as well as descending.
(d) Down the incline while ascending as well as descending.

I feel the frictional force should be down the incline while moving up and up the incline while moving down since friction opposes relative motion between the surfaces in contact. But my book says the answer is (B). Is it wrong?

Your book is correct. Perhaps if you draw a free body diagram and consider the forces acting on the cylinder the matter may become clearer.

ok I did that. the component of weight of the cylinder along the incline will be mgsin(theta). So since this force always acts down the plane, the frictional force will also always be directed up the incline?

But then, if the cylinder rolls up the incline, isn't there some other force that causes this? I mean, the cylinder will only roll up the incline if that force is greater than mgsin(theta).So the tendency of the cylinder is to move up the incline. and hence frictional force acts down the plane.. Please tell me where I am going wrong.

Last edited:
konichiwa2x said:
ok I did that. the component of weight of the cylinder along the incline will be mgsin(theta). So since this force always acts down the plane, the frictional force will also always be directed up the incline?

But then, if the cylinder rolls up the incline, isn't there some other force that causes this? I mean, the cylinder will only roll up the incline if that force is greater than mgsin(theta).So the tendency of the cylinder is to move up the incline. and hence frictional force acts down the plane.. Please tell me where I am going wrong.
Where does the question state that there is a force pushing it up the incline? If this was the case why would the cylinder stop and roll back down?

ok I get your point. But then, why does the cylinder roll up the plane in the first place??

Imagine the cylinder was set rolling by a force on a smooth horizontal surface, the cylinder then rolls along the surface at constant speed until it meets the incline at which point it experiences a force(s) and thus accelerates (down the incline). Does that make sense?

allright that makes sense. thanks a lot for your help

## 1. What is the force that is responsible for the movement of the cylinder up the inclined plane?

The force responsible for the movement of the cylinder up the inclined plane is gravity. As the cylinder is pushed or pulled up the incline, the force of gravity acts against it, causing it to move in the direction of the incline.

## 2. How does the angle of the inclined plane affect the movement of the cylinder?

The angle of the inclined plane affects the movement of the cylinder by changing the direction and magnitude of the force of gravity. The steeper the incline, the greater the force of gravity acting on the cylinder, making it more difficult to move up the incline.

## 3. Is the mass of the cylinder a factor in its movement up the inclined plane?

Yes, the mass of the cylinder does play a role in its movement up the inclined plane. The larger the mass of the cylinder, the greater the force of gravity acting on it, making it more difficult to move up the incline.

## 4. Can the cylinder ever reach the top of the inclined plane?

Yes, the cylinder can reach the top of the inclined plane if the force pushing or pulling it up the incline is greater than the force of gravity acting against it. However, as the angle of the incline increases, it becomes more difficult for the cylinder to reach the top.

## 5. How does friction affect the movement of the cylinder up the inclined plane?

Friction can have a significant impact on the movement of the cylinder up the inclined plane. If there is a high amount of friction between the cylinder and the incline, it will require more force to move the cylinder up the incline. However, if the friction is reduced, it will be easier for the cylinder to move up the incline.

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