Physics Chapter 5

An elevator is suspended from a cable. It is moving upward at a steady speed. Which is the correct free-body diagram for this situation?

B

Which of these objects is in equillibrium?
a) a car driving down the road at constant speed
b) a block sitting at rest on a table
c) a skydiver falling at a constant speed
d) all of the above

D) all of the above

You are riding in an elevator that is accelerating upward. Suppose you stand on a scale. The reading on the scale is
a) greater than your true weight
b) equal to your true weight
c) less than your true weight

A) greater than your true weight

In general, the coefficient of static friction is…
a) smaller than the coefficient of kinetic friction
b) equal to the coefficient of kinetic friction
c) greater than the coefficient of kinetic friction

c) greater than the coefficient of kinetic friction

The drag force pushes opposite your motion as you ride a bicycle. If you double your speed, what happens to the magnitude of the drag force?

the drag force increases

Two boxes are suspended from a rope over a pulley. Each box has weight 50 N. What is the tension in the rope?

50 N

A ring, seen from above, is pulled on by three forces. The ring is not moving. How big is the force F? (equation)

20sin(degree)*N

What are the components of w in the coordinate system shown?

D) Wx=-wsin(degree)
Wy= -wcos(degree)

A 50kg student (mg=490N) gets in a 1000 kg elevator at rest and stands on a metric bathroom scale. As the elevator accelerates upward, the scale reads….? (>,<,=)

>490N

A 50-kg student (mg = 490 N) gets in a 1000-kg elevator at rest and stands on a metric bathroom scale. Sadly, the elevator cable breaks. What is the reading on the scale during the few seconds it takes the student to plunge to his doom? (>,<,=)

zero N

The box is sitting on the floor of an elevator. The elevator is accelerating upward. The magnitude of the normal force on the box is

n>mg

A box is being pulled to the right at steady speed by a rope that angles upward. In this situation:

n<mg

A box on a rough surface is pulled by a horizontal rope with tension T. The box is not moving. In this situation:

f(s)=T

A box with a weight of 100 N is at rest. It is then pulled by a 30 N horizontal force. Does the box move?

No, 30N is less than f(s,max of 40N)

A box is being pulled to the right over a rough surface. T > f _k, so the box is speeding up. Suddenly the rope breaks.What happens?

the box slows steadily until it stops

Boxes A and B are sliding to the right on a frictionless surface. Hand H is slowing them. Box A has a larger mass than Box B. Considering only the horizontal forces:
A. F_{B on H} = F_{H on B} = F_{A on B} = F_{B on A}

B. F_{B on H} = F_{H on B} > F_{A on B} = F_{B on A}

C. F_{B on H} = F_{H on B} < F_{A on B} = F_{B on A}

D. F_{H on B} = F_{H on A} > F_{A on B}

B) F(BonH)=F(HonB) > F(AonB) =F(BonA)

Consider the situation in the figure. Which pair of forces is an action/reaction pair?

A. The tension of the string and the friction force acting on A

B. The normal force on A due to B and the weight of A

C. The normal force on A due to B and the weight of B

D. The friction force acting on A and the friction force acting on B

D) the friction force acting on A and the friction force acting on B
****

Boxes A and B are being pulled to the right on a frictionless surface; the boxes are speeding up. Box A has a larger mass than Box B. How do the two tension forces compare?

A. T₁ > T₂

B. T₁ = T₂

C. T₁ < T₂

D. Not enough information to tell

C. T1 < T2

The two masses are at rest. The pulleys are frictionless. The scale is in kg. The scale reads…

5kg

All three 50-kg blocks are at rest. The tension in rope 2 is
A. Greater than the tension in rope 1.

B. Equal to the tension in rope 1.

C. Less than the tension in rope 1.

b) equal to the tension in rope 1

The top block is accelerated across a frictionless table by the falling mass m. The string is massless, and the pulley is both massless and frictionless. The tension in the string is
A. T < mg

B. T = mg

C. T > mg

a) T<mg