You are using a wrench

to loosen a rusty nut.

Which arrangement will

be the most effective in

loosening the nut?

A

C D

B

E. All are equally effective

Two forces produce the

same torque. Does it follow

that they have the same

magnitude?

A. Yes

B. No

C. It depends

In which of the cases shown below is the torque provided by the applied force about the rotation axis biggest? For all cases the magnitude of the applied force is the same.

A. F1

B. F3

C. F4

D. All torques are the same

A force is applied to identical dumbbells for a certain period of time, first as in (a) and then as in (b). In which case does the dumbbell acquire the greater center-of-mass speed?

A. Case (a)B. Case (b)C. No differenceD. It depends on the rotational

inertia of the dumbbell.

A force is applied to identical dumbbells for a certain period of time, first as in (a) and then as in (b). In which case does the dumbbell acquire the greater kinetic energy?

A. Case (a)B. Case (b)C. No differenceD. It depends on the rotational

inertia of the dumbbell.

Two yo-yos are dropped from the same height. Each yo-yo has the same rotational inertia I.

Which yo-yo is moving faster when it hits the floor?

A B

C. It’s a tie.

A mass is hanging from the end of a horizontal bar which pivots about an axis through it center, but it being held stationary. The bar is released and begins to rotate.

As the bar rotates from horizontal to vertical, the magnitude of the torque on the bar…

A. increases B. decreases C. remains constant

A mass is hanging from the end of a horizontal bar which pivots about an axis through it center, but it being held stationary. The bar is released and begins to rotate.

As the bar rotates from horizontal to vertical, the magnitude of the angular momentum L of the bar…

A. increases B. decreases C. remains constant

+ –axis

A bar is subjected to four forces, all of the same magnitude, as shown. What is the sign of the torque about the axis of rotation? Use the sign convention shown.

A. The torque is zero B. positive (+) C. negative (–)

A door is pushed on by two forces, a large force at the door knob and a smaller force nearer the hinge as shown. The door does not move.

Assuming the hinge is well-greased (little or no friction there) is this situation as shown physically possible?

A. Sure, why not? B. No.

Two wheels with fixed axles, each have the same mass M, but wheel 2 has twice the radius of wheel 1. Each is accelerated from rest with a force applied as shown. In order to impart identical angular accelerations to both wheels, how much larger is F2 than F1?

A. F2 = F1

B. F2 = 2F1

C. F2 = 4F1

D. F2 = 8F1

E. None of these.

(Hints: I = M R2 for a hoop of mass M and radius R, and τ = I α)

A mass m is attached to a long , massless rod. The mass is close to one end of the rod. Is it easier to balance the rod on end with the mass near the top or near the bottom?

A. Easier with mass near top.B. Easier with mass near bottom.C. No difference.

A ladder of weight WL leans against a wall. The ladder has rollers at the top so that the wall exerts a normal force only on the top of the ladder. A person of weight WP slowly climbs the ladder. A free-body diagram for the ladder is shown.

As the person ascends the ladder, the force from the wall (Fwall)…A. increases.B. decreases.C. stays the same.

A ladder of weight WL leans against a wall. The ladder has rollers at the top so that the wall exerts a normal force only on the top of the ladder. A person of weight WP slowly climbs the ladder. A free-body diagram for the ladder is shown.

As the person ascends the ladder, the force of friction Fx, between the ladder and the ground...A. increases.B. decreases.C. stays the same.

A mass M is placed on a very light board supported at the ends, as shown. The free-body diagram shows directions of the forces, but not their correct relative sizes.What is the ratio FR/FL? (Hint: consider the torque about the mass M).

A. 2/3 B. 1/3 C. 1/2 D. 2 E. Some other value.

A mass m hangs from string wrapped around a pulley of radius R. The pulley has a moment of inertia I and its pivot is frictionless.

As the mass falls and the pulley rotates, the magnitude of the torque on the pulley is

A. greater than mgRB. less than mgRC. equal to mgR

(Hint: How does the tension in the string compare to mg?)

A box, with its center-of-mass off-center as indicated by the dot, is placed on an inclined plane. In which of the four orientations shown, if any, does the box tip over?

E. All are stable.