TEST 3: READING QUIZZES

the tension in cord A is greater than that in cord B

A 10.0-N weight is suspended by two cords as shown in Fig. 9-44. What can you say about the tension in the two cords?

60 kg

A 60-kg woman stands on the very end of a uniform board, of length l, which is supported one-quarter of the way from one end and is balanced (Fig. 9-41). What is the mass of the board? 15 kg. 20 kg. 30 kg. 60 kg. 120 kg

(e) Everywhere; the energy of the ball is the same at all of these points.

A ball is thrown straight up. At what point does the ball have the most energy? Ignore air resistance. (a) At the highest point of its path. (b) When it is rst thrown. (c) Just before it hits the ground. (d) When the ball is halfway to the highest point of its path. (e) Everywhere; the energy of the ball is the same at all of these points.

A- the potential energy decreases while the ball is going up

A ball is thrown straight up. Neglecting air resistance, which statement is NOT true regarding the energy of the ball? (a) The potential energy decreases while the ball is going up. (b) The kinetic energy decreases while the ball is going up. (c) The sum of the kinetic energy and potential energy is constant. (d) The potential energy decreases when the ball is coming down. (e) The kinetic energy increases when the ball is coming down.

b- 30 to 60 km/h

A car accelerates from rest to 30 km/h. Later, on a highway it accelerates from 30 km/h to 60 km/h. Which takes more energy, going from 0 to 30, or from 30 to 60?

4d

A car traveling at a velocity v can stop in a minimum distance d. What would be the car's minimum stopping distance if it were traveling at a velocity of 2v?

F is equal to only the x component of the tension in the cable.

A heavy ball suspended by a cable is pulled to the side by a horizontal force as shown in Fig. 9-43. If angle θ is small, the magnitude of the force F can be less than the weight of the ball because:

its potential energy increases and its kinetic energy remains the same.

A man pushes a block up an incline at a constant speed. As the block moves up the incline,

D- Increase the area of the columns by a factor of 8 by increasing their diameter by a factor of 2

A parking garage is designed for two levels of cars. To make more money, the owner decides to double the size of the garage in each dimension (length, width, and number of levels). For the support columns to hold up four floors instead of two, how should he change the columns' diameter? A- Double the area of the columns by increasing their diameter by a factor of 2. B- Double the area of the columns by increasing their diameter by a factor of 4 C- Quadruple the area of the columns by increasing their diameter by a factor of 2. D- Increase the area of the columns by a factor of 8 by increasing their diameter by a factor of 2 E- He doesn't need to increase the diameter of the columns.

2.0 cm

A rubber band is stretched by 1.0 cm when a force of 0.35 N is applied to each end. If instead a force of 0.70 N is applied to each end, estimate how far the rubber band will stretch from its unstretched length: A- 0.25cm B- 0.5cm C- 1.0cm D - 2.0cm

(c) No work is done if the direction of motion is perpendicular to the force.

A satellite in circular orbit around the Earth moves at constant speed. This orbit is maintained by the force of gravity between the Earth and the satellite, yet no work is done on the satellite. How is this possible? (a) No work is done if there is no contact between objects. (b) No work is done because there is no gravity in space. (c) No work is done if the direction of motion is perpendicular to the force. (d) No work is done if objects move in a circle.

c and d equally

A skier starts from rest at the top of each of the hills shown in Fig. 6-34. On which hill will the skier have the highest speed at the bottom if we ignore friction:

must be at least half the weight of the beam, no matter what the angle of the cable.

A uniform beam is hinged at one end and held in a horizontal position by a cable, as shown in Fig. 9-42. The tension in the cable

false

It is possible to do work on an object that remains at rest.

true

Potential Energy can sometimes be negative

(c) the height of the table, (d) the weight of the suitcase

Suppose you lift a suitcase from the oor to a table. The work you do on the suitcase depends on which of the following: (a) whether you lift it straight up or along a more complicated path, (b) the time the lifting takes, (c) the height of the table, (d) the weight of the suitcase

both hit the ground with the same speed

Two balls are thrown o a building with the same speed, one straight up and one at a 45° angle. Which statement is true if air resistance can be ignored?

rise

Two children are balanced on opposite sides of a seesaw. If one child leans inward toward the pivot point, her side will

B- Wire B stretches four times as much as wire A

Two steel wires have the same length and are under the same tension. But wire A has twice the diameter of wire B. Which of the following is true? A- Wire B stretches twice as much as wire A. B- Wire B stretches four times as much as wire A C- Wire A stretches twice as much as wire B. D- Wire A stretches four times as much as wire B. F- Both wires stretch the same amount

4

When the speed of your car is doubled, by what factor does its kinetic energy increase?

d- can be located anywhere

When you apply the torque equation ∑τ = 0 to an object in equilibrium, the axis about which torques are calculated a- must be located at a pivot. b- must be located at the object's center of gravity. c- should be located at the edge of the object. d- can be located anywhere.

the force of gravity & elastic force of a spring

Which of the following forces are conservative forces: A- Air resistance B- the force of gravity C- tension in the cord D- elastic force of a spring E- the force of water on a swimmer

A- the force of friction

You push a heavy crate down a ramp at a constant velocity. Only four forces act on the crate. Which force does the greatest magnitude of work on the crate? (a) The force of friction. (b) The force of gravity. (c) The normal force. (d) The force of you pushing. (e) The net force.

b- only if it starts moving

You push very hard on a heavy desk, trying to move it. You do work on the desk: (a) whether or not it moves, as long as you are exerting a force. (b) only if it starts moving. (c) only if it doesn't move. (d) never—it does work on you. (e) None of the above.

false

kinetic energy can be negative

B- the mass of the meter stick is equal to the Rock. EXPLAINED: The mass of the meter stick is equal to the mass of the rock. Since the meter stick is uniform, its center of mass is at the 50-cm mark. In terms of rotational motion about a pivot at the 25-cm mark, we can treat the stick as though its entire mass is concentrated at the center of mass. The meter stick's mass at the 50-cm mark (25 cm from the pivot) balances the rock at the 0 mark (also 25 cm from the pivot), so the masses must be equal.

A uniform meter stick supported at the 25-cm mark is in equilibrium when a 1-kg rock is suspended at the 0-cm end (as shown in Fig. 9-37). Is the mass of the meter stick greater than, equal to, or less than the mass of the rock? Explain your reasoning. A- the mass of the meter stick is greater than the Rock. B -the mass of the meter stick is equal to the Rock. C- the mass of the meter stick is less than the Rock.

E- much more than the woman's height

A woman is balancing on a high wire which is tightly strung, as shown in Fig. 9-45. The tension in the wire is A- about half the woman's weight. B- about twice the woman's weight. C- about equal to the woman's weight. D- much less than the woman's weight. E- much more than the woman's weight.

A- FA is down, FB is up, and FB is larger than FA .

A- FA is down, FB is up, and FB is larger than FA . B- Both forces are up and FB is larger than FA . C- FA is down, FB is up, and FA is larger than FB . D- Both forces are down and approximately equal. E- FB is down, FA is up, and they are equal.

C- the Young's modulus of the rope

As you increase the force that you apply while pulling on a rope, which of the following is NOT affected? A- The stress on the rope. B- The strain on the rope. C- The Young's modulus of the rope. D- All of the above. E- None of the above