5.06 Practice MC

A 0.5 kg ball with a rotational inertia of 0.1 kg*m² is rolling with an angular velocity of 20 rad/s. The radius of the ball is 0.2 m. What is the total kinetic energy of the ball?

• 20 J

• 24 J

• 4 J

• 5 J

• 6 J

A child is sitting on the outer edge of a carousel (like the one shown) which is spinning. If the child moves towards the center of the carousel, how will the angular velocity of the carousel change?

• The angular velocity will increase since the carousel must spin faster for the angular momentum to stay constant

• The angular velocity will increase because the rotational inertia of the system increased

• The angular velocity will stay constant since the angular momentum of the system must be conserved

• The angular velocity will decrease because the child exerted a net torque on the system which decreased its angular momentum.

• The angular velocity will decrease because the rotational inertia of the system decreased

A skater on ice begins to spin in the camel position, as shown in the figure to the left below. As she continues to spin, she straightens up, pulls her arms to her chest, and crosses her legs to spin in the corkscrew position, as shown in the figure. Air resistance and friction are negligible as the skater spins. Which of the following statements about the skater’s motion is true as she moves from the camel position to the corkscrew position?

• Her rotational kinetic energy increases because she does work on her arms and legs to bring them inward

• ​​​​​​Her rotational kinetic energy increases because her potential energy decreases.

• ​​​​​​Her rotational kinetic energy decreases because she does work on her arms and legs to bring them inward.

• ​​​​​​Her rotational kinetic energy decreases because her potential energy increases.

• ​​​​​​Her rotational kinetic energy remains the same because there is negligible frictional torque.

A ball of mass M rolls up a ramp at an angle of θ.

What is the magnitude of the normal force on the ball?

Four round objects of equal mass and radius roll without slipping along a horizontal surface that then bends upward and backward into an arc of half a circle. The objects all have the same linear speed initially. The objects are a hollow cylinder, a solid cylinder, a solid sphere, and a hollow sphere. Which of the following correctly lists the objects in order from the highest to the lowest max height reached on the arc?

• Hollow cylinder, hollow sphere, solid cylinder, solid sphere

• Hollow cylinder, solid sphere, solid cylinder, hollow sphere

• Solid sphere, solid cylinder, hollow sphere, hollow cylinder

• ​​​​​​​Solid sphere, hollow sphere, solid cylinder, hollow cylinder

• Hollow sphere, solid cylinder, hollow cylinder, solid sphere

• 32

• 16

• 8

• 4

• 1