All AP Physics 1 Resources
Example Questions
Example Question #31 : Circular And Rotational Motion
Two cars are racing side by side on a perfectly circular race track. The inner car is from the center of the track. The outer car is from center of the track.
If the outer car is moving at , determine it's angular momentum.
Example Question #32 : Circular And Rotational Motion
Moment of inertia of disk:
A car with wheels of mass and wheels of radius is traveling at . Treating the wheels as disks of uniform mass density, calculate the angular momentum of one wheel.
None of these
Finding angular velocity:
Using
and
Where is angular momentum
Combining equations and plugging in values:
Example Question #33 : Circular And Rotational Motion
A solid bowling ball of mass and radius is traveling at a linear velocity of . What is the angular momentum of the ball?
The expression for angular momentum is:
Where I is the moment of inertia for a solid sphere:
And w is the angular velocity:
Plugging these in, we get:
Plugging in our values, we get:
Example Question #11 : Angular Momentum
A bowling ball of mass and radius is traveling down a slope with a vertical height change of . If the ball starts from rest, what is the final linear velocity of the ball as it reaches the bottom of the slope? Neglect air resistance.
Let's begin with the expression for conservation of energy:
Since the ball begins from rest, we can eliminate initial kinetic energy. Also, if we assume that the bottom of the slope has a height of 0, we can eliminate final potential energy to get:
Plugging in expressions, we get:
Where I is the moment of inertia for a solid sphere:
And w is the angular velocity:
Plugging these in, we get:
Rearranging for final velocity, we get:
Plugging in our values, we get:
Example Question #11 : Angular Momentum
Two identical cars are racing side by side on a circular race track. Which has the greater angular momentum?
The inside car
The outside car
Impossible to determine
They are the same
The outside car
Where is the radius of the circle
is the mass of the object
is the linear velocity of the object
The car on the outside has a larger and a larger , and the same , thus it has a higher angular momentum.
Example Question #11 : Angular Momentum
A weight on a rope is swung around at until it comes into contact with a resting brick on flat ground. The brick travels . What is the coefficient of kinetic friction between the the brick and ground?
The first part of this problem is a transfer between angular and linear momentum. Conservation of momentum tells us that we can equate the angular momentum of the pendulum to the linear momentum of the brick, or , where and are the masses of the pendulum and brick respectively, is the angular velocity of the pendulum in , is the length of the pendulum rope, and is the resultant velocity of the brick. We find that the resulting velocity of the brick can be written as
The next part of the problem is identifying that the kinematic equations can be used here to find the acceleration the brick undergoes as it comes to a stop. Here we can use , where is the end velocity of the brick (zero), is the deceleration it undergoes, and is the distance the brick travels before coming to a stop. Solving for we have that .
Lastly, we know that the kinetic friction force can be written as . Newton's second law says that this can be written as . Thus we find that .
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