Object rolling down an incline

In summary, when an object, such as a cylinder, is rolling down an incline without slipping, there is some friction present and we need to find the velocity of the object. This can be done using either the force method, which involves calculating resultant force and using Newton's laws, or the energy method. Surprisingly, when using the energy method, we do not need to take into account the friction and our answer is still correct. The formula for finding the velocity in this scenario is v = sqrt(4*s*g*sinθ/3), where m is the mass, r is the radius of the cylinder, I is the moment of inertia, s is the distance traveled, θ is the angle of incline, and g
  • #1
RRachev
5
0
An object (for example cylinder) is rolling down an incline, with no slip. We know there is some friction and we have to find the velocity of the objects. There are 2 ways of doing so with calculating resultant force and using Newton's laws and the energy method. Why is it that when we are using the energy method we don't have to take into account the friction and our answer is still right?

Mass - m
Radius of the cylinder - r
Moment of Inertia - I=(mr^2)/2
Distance traveled - s
Angle of Incline - θ
Acceleration due to gravity- g

I know the answer is v= sqrt(4*s*g*sinθ/3)

Thanks in advance
 
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  • #2
What type of friction is present, kinetic or static?
 
  • #3
The question did not say. But when you compute the velocity using the force method or the energy method (while using the second one assume no friction force) and the answer is the same. I do not quite understand the solution probably that's the problem itself.
 
  • #4
The problems inadvertently says it, I'm asking what your interpretation of the problem is, do you think the friction keeping the cylinder from slipping is kinetic or static?
 
  • #5
Ohh now I see what you mean. Should be static?
 
  • #6
Correct. Can static friction do work on an object?
 
  • #7
No.
Yeah thanks a lot for the help.
 

Related to Object rolling down an incline

1. How does the angle of the incline affect the speed of the object rolling down?

The steeper the incline, the faster the object will accelerate and gain speed. This is because gravity has a greater effect on the object when it is rolling down a steeper incline.

2. What is the relationship between the mass of the object and its acceleration down an incline?

The mass of the object does not have a direct effect on its acceleration down an incline. It is the force of gravity and the angle of the incline that determine the acceleration of the object.

3. How does friction affect the motion of the object rolling down an incline?

Friction acts as a resisting force and will slow down the object's motion down the incline. The rougher the surface of the incline, the greater the friction force, and the slower the object will move.

4. What is the difference between a rolling object and a sliding object down an incline?

A rolling object has both translational and rotational motion, while a sliding object only has translational motion. This means that a rolling object will have a greater acceleration down the incline due to its rotational motion.

5. How is the final velocity of the object calculated at the bottom of the incline?

The final velocity of the object can be calculated using the equation vf = vi + at, where vf is the final velocity, vi is the initial velocity (usually 0 for an object starting at rest), a is the acceleration, and t is the time the object takes to reach the bottom of the incline. This assumes that there is no friction present.

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