# Angular Momentum/Rotation Problem

• Felix83
In summary, a billiard ball with a radius of 7.00 cm is hit from the horizontal direction at a point h above its center. It then begins to move with a velocity of 15.0 m/s, and has a kinetic coefficient of 0.214 with the table. To roll without slipping at a speed of 14.10 m/s, the value of h should be determined.
Felix83
A uniform billiard ball with radius R= 7.00 cm rests on a billiard table. At one moment, the ball received a hit from the horizontal direction. Hit point is h above the center of the ball. Then, the ball begins to move with a velocity V0= 15.0 m/s. The kinetic coeffient between table and the slipping ball is 0.214. In order that the ball can roll without slipping with a speed V= 14.10 m/s, what the value of h should be?

I'm stumped on this one, I tried several different ways, all of which the computer tells me is wrong. But the numbers I got didn't make any sense anyway. Any ideas?

How about you post yours...?To see where they went wrong.

Daniel.

It seems like there may be a misunderstanding of the problem here. The question is asking for the value of h, which is the hit point above the center of the ball, in order for the ball to roll without slipping with a speed of 14.10 m/s. This means that the ball will be rolling and not sliding on the table. The initial velocity given (V0=15.0 m/s) is not relevant for this part of the problem.

To solve this problem, we can use the equation for rolling motion without slipping: V=ωR, where V is the linear velocity of the ball, ω is the angular velocity, and R is the radius of the ball. We also know that the kinetic coefficient (μ) between the ball and the table is 0.214.

First, we can find the angular velocity of the ball at a speed of 14.10 m/s by rearranging the equation: ω=V/R. Plugging in the values, we get ω=14.10 m/s ÷ 0.07 m = 201.43 rad/s.

Next, we can use the definition of kinetic coefficient to find the frictional force (F) acting on the ball: F=μmg, where m is the mass of the ball and g is the acceleration due to gravity. We can find the mass of the ball by using the formula for the volume of a sphere: V=4/3πR³. Plugging in the values, we get m=4/3π(0.07 m)³ρ, where ρ is the density of the ball. We can assume a density of 1 g/cm³ for a billiard ball, so m=0.229 kg. Plugging this into the equation for frictional force, we get F=0.214(0.229 kg)(9.8 m/s²)=0.48 N.

Finally, we can use the definition of torque (τ) to find the distance h: τ=FR, where R is the radius of the ball. Plugging in the values, we get τ=0.48 N(0.07 m)=0.0336 Nm. We also know that τ=Iα, where I is the moment of inertia of the ball and α is the angular acceleration. The moment of inertia for a solid sphere is 2/5MR², so I

## 1. What is angular momentum and how is it related to rotation?

Angular momentum is a physical quantity that measures the amount of rotational motion an object has. It is related to rotation because it is the product of an object's moment of inertia and its angular velocity.

## 2. How is angular momentum conserved in a closed system?

In a closed system, the total angular momentum remains constant. This means that if one object in the system increases its angular momentum, another object must decrease its angular momentum by an equal amount in order to keep the total angular momentum the same.

## 3. What is the difference between angular momentum and linear momentum?

Angular momentum is a measurement of rotational motion, while linear momentum is a measurement of linear motion. Angular momentum takes into account an object's mass, speed, and distance from the axis of rotation, while linear momentum only considers an object's mass and velocity.

## 4. How does the distribution of mass affect an object's moment of inertia?

The moment of inertia is a measurement of an object's resistance to rotational motion. The distribution of mass within an object can greatly affect its moment of inertia, with objects that have more mass concentrated towards the axis of rotation having a lower moment of inertia compared to objects with more mass distributed farther from the axis of rotation.

## 5. How do external torques affect an object's angular momentum and rotation?

An external torque can cause a change in an object's angular momentum, which will in turn affect its rotation. If the torque is in the same direction as the angular momentum, the object will experience an increase in rotational speed. If the torque is in the opposite direction, the object will experience a decrease in rotational speed or may even stop rotating altogether.

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