Honors Physics Exam Review pt. 1

The original Ferris wheel had a radius of 38 m and completed a full revolution (2𝜋 radians) every two minutes when operating at its maximum speed. If the wheel were uniformly slowed from its maximum speed to a stop in 35 seconds, what would be the magnitude of the tangential acceleration at the outer rim of the wheel during its deceleration?

0.057 m/s^2

A horizontal, 10-m plank weighs 100 N. It rests on two supports that are placed 1.0 m from each end as shown in the figure. How close to one end can an 800-N person stand without causing the plank to tip?

0.5 m

A grindstone of radius 4.0 m is initially spinning with an angular speed of 8.0 rad/s. The angular speed is then increased to 12 rad/s over the next 4.0 seconds. Assume that the angular acceleration is constant. What is the magnitude of the angular acceleration of the grindstone?

1.0 rad/s^2

A 2.0-kg solid disk rolls without slipping on a horizontal surface so that its center proceeds to the right with speed 5.0 m/s. The point A is the uppermost point on the disk and the point B is along the horizontal line that connects the center of the disk to the rim. What is the instantaneous speed of point A with respect to the ground?

10.0 m/s

An 80-kg man balances the boy on a teeter-totter as shown. Note: Ignore the weight of the board. What is the approximate mass of the boy?

20 kg

During the spin-dry cycle of a washing machine, the motor slows from 90 rad/s to 30 rad/s while the turning the drum through an angle of 180 radians. What is the magnitude of the angular acceleration of the motor?

20 rad/s^2

One end of a rope is tied to the handle of a horizontally-oriented and uniform door. A force vector F is applied to the other end of the rope as shown in the drawing. The door has a weight of 145 N and is hinged on the right. What is the maximum magnitude of vector F for which the door will remain at rest?

265 N

Consider four point masses located as shown in the sketch. The acceleration due to gravity is the same everywhere. What is the x coordinate of the center of gravity for this system?h

3.0 m

A wheel turns through an angle of 188 radians in 8.0 s; and its angular speed at the end of the period is 44 rad/s. If the angular acceleration is constant, what was the angular speed of the wheel at the beginning of the 8.0 s interval?

3.0 rad/s

A 3.0-kg ball and a 1.0-kg ball are placed at opposite ends of a massless beam so that the system is in equilibrium as shown. Note: The drawing is not drawn to scale. What is the value of the ratio of the lengths, b/a?

4.0

A 2.0-kg solid disk rolls without slipping on a horizontal surface so that its center proceeds to the right with speed 5.0 m/s. The point A is the uppermost point on the disk and the point B is along the horizontal line that connects the center of the disk to the rim. What is the instantaneous speed of point B with respect to the ground?

7.1 m/s

On an amusement park ride, passengers are seated in a horizontal circle of radius 7.5 m. The seats begin from rest and are uniformly accelerated for 21 seconds to a maximum rotational speed of 1.4 rad/s. What is the instantaneous tangential speed of the passengers 15 s after the acceleration begins?

7.5 m/s

Three children are pulling on a rotatable platform on a playground. The platform has a radius of 3.80 m. In the picture, two children are pulling with equal forces of 40.0 N in an attempt to make the platform rotate clockwise. The third child applies a force of 60 N as shown. What is the net torque on the platform? Note: "ccw" is counterclockwise and "cw" is clockwise.

76 Nm, cw

The drawing shows the top view of a door that is 1.68 m wide. Two forces are applied to the door as indicated. What is the magnitude of the net torque on the door with respect to the hinge?

8.3 Nm

Two points are located on a rigid wheel that is rotating with decreasing angular velocity about a fixed axis. Point A is located on the rim of the wheel and point B is halfway between the rim and the axis. Which one of the following statements concerning this situation is true?

Both points have the same instantaneous angular velocity.

Complete the following statement: When a net torque is applied to a rigid object, it always produces a

Change on angular velocity.

A circular hula hoop rolls upright without slipping on a flat horizontal surface. Which one of the following statements is necessarily true?

Every point on the rim of the wheel has a different velocity.

Which one of the following statements concerning the moment of inertia I is false?

I depends on the angular acceleration of the object as it rotates

Complete the following statement: A body is in translational equilibrium

If it is either at rest or moving with constant velocity.

Consider the following four objects: a hoop, a flat disk, a solid sphere, and a hollow sphere. Each of the objects has mass M and radius R. The axis of rotation passes through the center of each object, and is perpendicular to the plane of the hoop and the plane of the flat disk. Which of these objects requires the largest torque to give it the same angular acceleration?

The Hoop

Which one of the following statements concerning a wheel undergoing ideal rolling motion is true?

There is no slipping at the point where the wheel touches the surface on which it is rolling.

NEEDS TO BE MOVED TO #13 A 2.0-kg solid disk rolls without slipping on a horizontal surface so that its center proceeds to the right with speed 5.0 m/s. The point A is the uppermost point on the disk and the point B is along the horizontal line that connects the center of the disk to the rim. What is the instantaneous speed of the point of the disk that makes contact with the surface?

Zero m/s

A wrench is used to tighten a nut as shown in the figure. A 12-N force is applied 7.0 cm from the axis of rotation. What is the magnitude of the torque due to the applied force?

0.84 Nm

A string is wrapped around a pulley of radius 0.20 m and moment of inertia 0.40 kg · m2. The string is pulled with a force of 28 N. What is the magnitude of the resulting angular acceleration of the pulley?

14 rad/s^2

A massless frame in the shape of a square with 2-m sides has a 1-kg ball at each corner. What is the moment of inertia of the four balls about an axis through the corner marked O and perpendicular to the plane of the paper?

16 kgm^2

A certain merry-go-round is accelerated uniformly from rest and attains an angular speed of 1.2 rad/s in the first 18 seconds. If the net applied torque is 1200 N · m, what is the moment of inertia of the merry-go-round?

18,000 kgm^2

A long thin rod of length 2L rotates with a constant angular acceleration of 8.0 rad/s2 about an axis that is perpendicular to the rod and passes through its center. What is the ratio of the angular speed (at any instant) of a point on the end of the rod to that of a point a distance L/2 from the end of the rod?

1:1

In the drawing shown, the large wheel has a radius of 7.1 m. A rope is wrapped around the edge of the wheel and a 7.6 kg-box hangs from the rope. A smaller disk of radius 1.38 m is attached to the wheel. A rope is wrapped around the edge of the disk as shown. An axis of rotation passes through the center of the wheel-disk system. What is the value of the mass M that will prevent the wheel from rotating?

39 kg

A uniform 13-kg trap door is oriented horizontally and hinged as shown. What is the magnitude of the torque on the door at the instant that the release is activated and the door can freely rotate?

48 Nm

A 66-N · m torque acts on a wheel with a moment of inertia 175 kg · m2. If the wheel starts from rest, how long will it take the wheel to make one revolution?

5.8 s