Angular impulse of rolling ball

In summary, the conversation discusses using the angular impulse method to find an expression for the initial linear speed (v) when pure rolling starts for a sliding sphere meeting a floor with friction. There is a discrepancy in the problem involving the use of "R" instead of "r" and "Vi=V" instead of "Vi=Vf". The issue of mv being larger than the impulse given is also addressed. It is suggested to properly distinguish initial and final linear speeds to clarify the relationship between them.
  • #1
serverxeon
101
0
In the following, we have a sliding sphere, when it meets a floor with friction.

I want to use the angular impulse method to find an expression of the v when pure rolling starts.

5wmn8z.jpg


[sorry I have no idea how to type in latex.]

This is obviously incorrect.
But I can't find out what's wrong. anyone?
 
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  • #2
Why is that obviously wrong? I at least could follow it. (Small note: you changed from r to R in the problem. Also I think Vi should equal Vi not Vi=V because if Vi=V that's like Vi=Vf, but that's more of a typo.)
 
Last edited:
  • #3
it's wrong cos it states that mv is larger tahn the impulse given.
 
  • #4
?? Kind of following. Why does that matter? The value of mv can be bigger than the linear impulse in this problem. (Note: where mv=mVfinal)
 
  • #5
It might become clearer if you properly distinguish initial and final linear speeds (u, v perhaps) and get the relationship between them.
 

1. What is angular impulse?

Angular impulse is a measure of how much a rotational motion changes over time. It is the product of a force applied to an object and the time duration of that force.

2. How is angular impulse related to a rolling ball?

Angular impulse is important in understanding the motion of a rolling ball because it affects the rotation of the ball. When a force is applied to the ball, it causes a change in angular momentum, which affects how the ball rolls.

3. What factors influence the angular impulse of a rolling ball?

The main factor that influences the angular impulse of a rolling ball is the magnitude and direction of the applied force. The location of the force on the ball's surface and the time duration of the force also play a role.

4. How is angular impulse calculated?

Angular impulse can be calculated by multiplying the force applied to an object by the time duration of that force. In the case of a rolling ball, the force is typically applied as a torque, which is the product of the force and the distance from the axis of rotation.

5. How does angular impulse affect the stability of a rolling ball?

Angular impulse plays a crucial role in the stability of a rolling ball. If a force is applied at the center of mass of the ball, the ball will experience a pure translational motion and remain stable. However, if the force is applied at a different point, it can cause the ball to wobble or change its direction of motion, leading to instability.

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