Physics Unit 7 & 8 Concept Quizzes

In which of the following scenarios is no net work done? a A car accelerates down a hill. b A car travels at constant speed on a flat road. c A car decelerates as it travels up a hill. d A car decelerates on a flat road.

b A car travels at constant speed on a flat road.

If the work output of a machine is always less than the work input, where does the missing work go? a It is used to get the machine started. b It is used to overcome the friction created by the machine. c It is used to keep the machine running. d There isn't enough power present.

b It is used to overcome the friction created by the machine.

Which of the following are not units of power? a hp b J c W d J/s

b J

If you exert 20 N of force on a screwdriver and it exerts 40 N on a paint can lid, what is the screwdriver's mechanical advantage? a 2 b 20 c 1 d 40

a 2

Car J moves twice as fast as car K, and car J has half the mass of car K. The kinetic energy of car J, compared to car K is a 2 to 1. b 1 to 2. c the same. d 4 to 1.

a 2 to 1.

At what rate is a 60.0-kg boy using energy when he runs up a flight of stairs 10.0-m high, in 8.00 s? a 735 W b 75.0 W c 48 W d 4.80 kW

a 735 W

What are the units for a spring constant? a N/m b N m c N d m

a N/m

A container of water is lifted vertically 3.0 m then returned to its original position. If the total weight is 30 N, how much work was done? a No work was done. b 90 J c 45 J d 180 J

a No work was done.

In which of the following sentences is work used in the scientific sense of the word? a Sam and Rachel pushed hard, but they could do no work on the car. b Holding a heavy box requires a lot of work. c John learned that shoveling snow is hard work. d A scientist works on an experiment in the laboratory.

a Sam and Rachel pushed hard, but they could do no work on the car.

You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down. a Work is - on the way up and + on the way down. b Work is + on the way up and + on the way down. c Work is - on the way up and - on the way down. d Work is + on the way up and - on the way down.

a Work is - on the way up and + on the way down.

Is it possible for a system to have negative potential energy? a Yes, since the choice of the zero of potential energy is arbitrary. b No, because the kinetic energy of a system must equal its potential energy. c Yes, as long as the total energy is positive. d No, because this would have no physical meaning.

a Yes, since the choice of the zero of potential energy is arbitrary.

An object is released from rest a height h above the ground. A second object with four times the mass of the first if released from the same height. The potential energy of the second object compared to the first is a four times as much. b twice as much. c one-half as much. d one-fourth as much.

a four times as much.

Which of the following causes machines not to be 100% efficient? a friction b input force c output force d power

a friction

If the net work done on an object is positive, then the object's kinetic energy a increases. b decreases. c is zero. d remains the same.

a increases.

A force does work on an object if a component of the force a is parallel to the displacement of the object. b is perpendicular to the displacement of the object. c perpendicular to the displacement of the object moves the object along a path that returns the object to its starting position. d parallel to the displacement of the object moves the object along a path that returns the object to its starting position.

a is parallel to the displacement of the object.

What is the correct unit of work expressed in SI units? a kg m2/s2 b kg m/s2 c kg m2/s d kg2 m/s2

a kg m2/s2

What is the correct unit of power expressed in SI units? a kg m2/s3 b kg m/s2 c kg2 m/s2 d kg m2/s2

a kg m2/s3

Which of the following in the comparison of a machine's work output with the work input? a mechanical efficiency b force c mechanical advantage d power

a mechanical efficiency

Work is done when a the displacement is not zero. b the force and displacement are perpendicular. c the force is zero. d the displacement is zero.

a the displacement is not zero.

The quantity 1/2 mv^2 is a the kinetic energy of the object. b the potential energy of the object. c the power supplied to the object by the force. d the work done on the object by the force.

a the kinetic energy of the object.

If the mass in a horizontal mass-spring system was doubled, the elastic potential energy in the system would change by a factor of a 1/2. b 0 (no change). c 4. d 2.

b 0 (no change).

How many joules of energy are used by a 1.0 hp motor that runs for 1.0 hr? (1 hp = 746 W) a 3.6 ×10^3 J b 2.7 ×10^6 J c 4.8 J d 4.5 ×10^4 J

b 2.7 ×10^6 J

In which of the following scenarios is work done? a A construction worker carries a heavy beam while walking at constant speed along a flat surface. b A car decelerates while traveling on a flat stretch of road. c A student holds a spring in a compressed position. d A weightlifter holds a barbell overhead for 2.5 s.

b A car decelerates while traveling on a flat stretch of road.

Two children are on a merry-go-round. Billy is a distance r from the center and Willy is a distance 3r from the center. What is the ratio of Willy's centripetal acceleration to Billy's centripetal acceleration? A 3 B 9 C 1/3 D 1

A 3

The movement of an object or a point mass at a constant speed around a circle that has a fixed radius is called uniform: A circular motion B parabolic motion C elliptical motion D rotational motion

A circular motion

When an object experiences uniform circular motion, the direction of the net force is A is directed toward the center of the circular path. B in the opposite direction of the motion of the object. C is directed away from the center of the circular path. D in the same direction as the motion of the object.

A is directed toward the center of the circular path.

Horses that move with the fastest linear speed on a merry-go-round are located A near the outside. B near the center. C anywhere, because they all move at the same speed. D higher above the ground

A near the outside.

An object is placed exactly halfway between the Earth and moon. The object will fall toward the A moon. B Earth. C none of these D Sun

B Earth.

In this text, which of the following symbols represents the constant of universal gravitation? A F_g B G C g D F_c

B G

Two children are on a merry-go-round. Which child has the faster linear speed? A The child near the center. B The child near the edge. C They both have the same speed. D Impossible to say without knowing the angular speed.

B The child near the edge.

Two children are on a merry-go-round. Which child has the greater centripetal acceleration? A The child near the center. B The child near the edge. C They both have the same centripetal acceleration. D Impossible to say without knowing the linear speed.

B The child near the edge.

Two children of equal mass are on a merry-go-round. Which child experiences the greater centripetal force? A The child near the center. B The child near the edge. C They both have the same centripetal force. D Impossible to say without knowing the linear speed.

B The child near the edge.

An object moves in a circular path at a constant speed. Compare the direction of the object's velocity and acceleration vectors. A Both vectors point in the same direction. B The vectors are perpendicular. C The vectors point in opposite directions. D The question is meaningless, since the acceleration is zero.

B The vectors are perpendicular.

The amount of gravitational force that acts on the space shuttle while in orbit is A the same as the shuttle's weight on the Earth's surface. B almost as much as the shuttle's weight on the Earth's surface. C nearly zero. D more than the shuttle's weight on the Earth's surface.

B almost as much as the shuttle's weight on the Earth's surface.

A supplier wants to make a profit by buying metal by weight at one altitude and selling it at the same price per pound at another altitude. The supplier should D A buy at a low altitude and sell at a high altitude. B buy at a high altitude and sell at a low altitude. C disregard altitude because it makes no difference. D buy at night and sell during the day

B buy at a high altitude and sell at a low altitude.

Why does an astronaut weigh less on the moon than on Earth? A The astronaut has less mass on the moon. B The astronaut is farther from Earth's center when he or she is on the moon. C The gravitational field strength is less on the moon's surface than on Earth's surface. D The astronaut is continually in free fall because the moon orbits Earth.

C The gravitational field strength is less on the moon's surface than on Earth's surface.

Two children are on a merry-go-round. Which child has the faster angular speed? A The child near the center. B The child near the edge. C They both have the same speed. D Impossible to say without knowing the linear speed.

C They both have the same speed.

Is it possible for an object moving with a constant speed to accelerate? Explain. A Yes, if an object is moving it can experience acceleration B No, if the speed is constant then the acceleration is equal to zero. C Yes, although the speed is constant, the direction of the velocity can be changing. D No, an object can accelerate only if there is a net force acting on it.

C Yes, although the speed is constant, the direction of the velocity can be changing.

What force is needed to make an object move in a circle? A static friction B kinetic friction C centripetal force D weight

C centripetal force

What is the term for the net force directed toward the center of an object's circular path? A circular force B centrifugal force C centripetal force D orbital force

C centripetal force

In this text, which of the following symbols represents gravitational field strength? A F_g B G C g D F_c

C g

When an object is moving with uniform circular motion, the object's tangential speed A is circular. B is perpendicular to the plane of motion. C is constant. D is directed toward the center of motion.

C is constant.

When an object experiences uniform circular motion, the direction of the acceleration is A in the same direction as the velocity vector. B is directed away from the center of the circular path. C is directed toward the center of the circular path. D in the opposite direction of the velocity vector.

C is directed toward the center of the circular path.

The equation for the speed of an object in circular orbit is v_t = {square root of}(G x m/r) G mr . What does m represent in this equation? A the mass of the sun B the mass of Earth C the mass of the central object D the mass of the orbiting object

C the mass of the central object

According to Kepler's second law of planetary motion, A planets maintain constant speed around the Sun. B planets maintain constant acceleration around the Sun. C the speed of a planet is greatest when it is closest to the Sun. D the area swept out by the orbit per time unit keeps changing.

C the speed of a planet is greatest when it is closest to the Sun.

A car goes around a curve of radius r at a constant speed v. What is the direction of the net force on the car? A toward the front of the car B away from the curve's center C toward the curve's center D toward the back of the car

C toward the curve's center

Two children are on a merry-go-round. Billy is a distance r from the center and Willy is a distance 3r from the center. What is the ratio of Willy's period of revolution to Billy's period of revolution? A 3 B 9 C 1/3 D 1

D 1

Suppose the circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second when you are riding the bicycle, then your speed will be A 3.14 m/s. B 3 m/s. C 6.28 m/s. D 2 m/s. E 1 m/s.

D 2 m/s.

A 1.00-kg ball is attached to a string of 0.50 m and swung in a horizontal circle with a velocity of 2.00 m/s. Find the centripetal acceleration. A 0.25 m/s2 B 2.0 m/s2 C 4.0 m/s2 D 8.0 m/s2

D 8.0 m/s^2

Which of the following can be a centripetal force? A friction B gravity C tension D all of the above

D all of the above

What type of acceleration does an object moving with constant speed in a circular path experience? A linear acceleration B free fall C constant acceleration D centripetal acceleration

D centripetal acceleration

According to Newton, doubling the distance between two interacting objects A divides by 2 the gravitational force between them. B multiplies by 2 the gravitational force between them. C multiplies by 4 the gravitational force between them. D divides by 4 the gravitational force between them.

D divides by 4 the gravitational force between them.

Two objects move toward each other because of gravity. As the objects get closer and closer, the force between them A increases, then decreases. B remains constant. C decreases. D increases. E decreases, then increases.

D increases.

A ball is whirled on a string, then the string breaks. What causes the ball to move off in a straight line? A centripetal acceleration B centripetal force C centrifugal force D inertia

D inertia

When a car makes a sharp left turn, what causes the passengers to move toward the right side of the car? A centripetal acceleration B centripetal force C centrifugal force D inertia

D inertia

When an object is moving with uniform circular motion, the centripetal acceleration of the object A is circular. B is perpendicular to the plane of motion. C is zero. D is directed toward the center of motion.

D is directed toward the center of motion.

The reason the moon does not crash into the Earth is that the A Earth's gravitational field is weak at the moon. B gravitational pull of other planets keeps the moon up. C moon has less mass than the Earth. D moon has a sufficient tangential speed. E none of these

D moon has a sufficient tangential speed.

What prevents satellites such as the space shuttle from falling? A gravity B centripetal force C the absence of air drag D centrifugal force E Nothing; they are continually falling as they orbit the Earth.

E Nothing; they are continually falling as they orbit the Earth.

A worker does 25 J of work lifting a bucket, then sets the bucket back down in the same place. What is the total net work done on the bucket? a 0 J b 50 J c 25 J d -25 J

a 0 J

Which of the following formulas would be used to directly calculate the kinetic energy of an object with mass m bouncing up and down on a spring with spring constant k? a KE = − 1/2mv^2 b KE = 1/2mv^2 c KE = 1/2kx^2 d KE = −1/2kx^2

b KE = 1/2mv^2

Can work be done on a system if there is no motion? a Yes, if an outside force is provided. b No, because of the way work is defined. c No, since a system which is not moving has no energy. d Yes, since motion is only relative.

b No, because of the way work is defined.

Which of the following is a true statement about the conservation of energy? a Mechanical energy is always conserved. b Total energy is always conserved. c Potential energy is always conserved. d Kinetic energy is always conserved.

b Total energy is always conserved.

Gravitational potential energy is always measured in relation to a kinetic energy. b a zero level. c mechanical energy. d total potential energy.

b a zero level.

If the net work done on an object is negative, then the object's kinetic energy a is zero. b decreases. c increases. d remains the same.

b decreases.

When a machine increases the size of the force exerted, what happens to the distance? a it must increase b it must decrease c it must stay the same d it must double

b it must decrease

Which of the following energy forms is associated with an object in motion? a elastic potential energy b kinetic energy c nonmechanical energy d potential energy

b kinetic energy

Which of the following energy forms is associated with an object due to its position? a positional energy b potential energy c kinetic energy d total energy

b potential energy

On a plot of Force versus position (F vs. x), what represents the work done by the force F? a the slope of the curve b the area under the curve c the length of the curve d the product of the maximum force times the maximum x

b the area under the curve

What does a fixed pulley change? a the speed of a force b the direction of a force c the size of a force d the timing of the force

b the direction of a force

The quantity mgh is a the work done on the object by the force. b the gravitational potential energy of the object. c the power supplied to the object by the force. d the kinetic energy of the object.

b the gravitational potential energy of the object.

What is the work that you do on a machine? a power b work input c work output d lever

b work input

If you walk 5.0 m horizontally forward at a constant velocity carrying a 10-N object, the amount of work you do is a less than 50 J, but more than 0 J. b zero. c more than 50 J. d equal to 50 J.

b zero.

A 50-N object was lifted 2.0 m vertically and is being held there. How much work is being done in holding the box in this position? a 100 J b less than 100 J, but more than 0 J c 0 J d more than 100 J

c 0 J

A child moving at constant velocity carries a 2 N ice-cream cone 1 m across a level surface. What is the net work done on the ice-cream cone? a 0.5 J b 20 J c 0 J d 2 J

c 0 J

An object hits a wall and bounces back with half of its original speed. What is the ratio of the final kinetic energy to the initial kinetic energy? a 1/2 b 4 c 1/4 d 2

c 1/4

A brick is moving at a speed of 3 m/s and a pebble is moving at a speed of 5 m/s. If both objects have the same kinetic energy, what is the ratio of the brick's mass to the rock's mass? a 5 to 3 b 12.5 to 4.5 c 25 to 9 d 3 to 5

c 25 to 9

Ball A has triple the mass and speed of ball B. What is the ratio of the kinetic energy of ball A to ball B. a 6 b 9 c 27 d 3

c 27

If the displacement of a horizontal mass-spring system was doubled, the elastic potential energy in the system would change by a factor of a 1/2. b 1/4. c 4. d 2.

c 4.

A 10-N force is needed to move an object with a constant velocity of 5.0 m/s. What power must be delivered to the object by the force? a 0.50 W b 100 W c 50 W d 1.0 W

c 50 W

A cyclist does work at the rate of 500 W while riding. How much force does her foot push with when she is traveling at 8.0 m/s? a 31 N b 80 N c 63 N d 4000 N

c 63 N

How does a ramp make lifting a heavy object easier? a The object is moved over a shorter distance. b The ramp increases the amount of work you do. c Less force is needed to move the object over a longer distance. d More force is needed to move the object over a longer distance.

c Less force is needed to move the object over a longer distance.

A truck weighs twice as much as a car, and is moving at twice the speed of the car. Which statement is true about the truck's kinetic energy compared to that of the car? a The truck has 4 times the kinetic energy of the car. b All that can be said is that the truck has more kinetic energy. c The truck has 8 times the kinetic energy of the car. d The truck has twice the kinetic energy of the car.

c The truck has 8 times the kinetic energy of the car

What is the common formula for work? Assume that W is the work, F is a constant force, v is the change in velocity, and d is the displacement. a W = Fd^2 b W = F^2d c W = Fd d W = F(delta)v

c W = Fd

Which of the following machines always has a mechanical advantage of less than 1? a wheel and axle b third-class lever c a long, thin wedge d a poorly lubricated, movable pulley

c a long, thin wedge

If you push twice as hard against a stationary brick wall, the amount of work you do a is cut in half. b doubles. c remains constant at zero. d remains constant but non-zero.

c remains constant at zero.

What is the work done by a machine on an object? a power b work input c work output d lever

c work output

The area under the curve, on a Force versus position (F vs. x) graph, represents a kinetic energy. b potential energy. c work. d power.

c work.

An acorn falls from a tree. Compare its kinetic energy K, to its potential energy U. a K decreases and U increases. b K decreases and U decreases. c K increases and U increases. d K increases and U decreases.

d K increases and U decreases.

Describe the energy of a car driving up a hill. a entirely potential b entirely kinetic c gravitational d both kinetic and potential

d both kinetic and potential

What is a machine that is made of two simple machines? a simple machine b lever c pulley d compound machine

d compound machine

The main difference between kinetic energy and potential energy is that a although both energies involve motion, only kinetic energy involves position. b although both energies involve position, only potential energy involves motion. c kinetic energy involves position, and potential energy involves motion. d kinetic energy involves motion, and potential energy involves position.

d kinetic energy involves motion, and potential energy involves position.

What is the number of times the machine multiplies force? a power b output force c mechanical efficiency d mechanical advantage

d mechanical advantage

Which of the following would increase the mechanical advantage of a first-class lever? a applying a greater input force b increasing the rate at which force is applied c decreasing the load d moving the fulcrum closer to the load

d moving the fulcrum closer to the load

Which of the following is the rate at which energy is transferred? a potential energy b kinetic energy c mechanical energy d power

d power

If the net work done on an object is zero, then the object's kinetic energy a increases. b is zero. c decreases. d remains the same.

d remains the same.

If the sign of work is negative, a the displacement is in the same direction as the force. b the displacement is perpendicular to the force. c no work is done. d the displacement is in the direction opposite the force.

d the displacement is in the direction opposite the force.

The quantity 1/2 kx^2 is a the power supplied to the object by the force. b the work done on the object by the force. c the kinetic energy of the object. d the elastic potential energy of the object.

d the elastic potential energy of the object.

The quantity Fd/t is a the potential energy of the object. b the work done on the object by the force. c the kinetic energy of the object. d the power supplied to the object by the force.

d the power supplied to the object by the force.

Of the following, which is not a unit of power? a newton-meter/second b watt c joule/second d watt/second

d watt/second

By comparing the mechanical advantage of two machines, what can you tell about the machine? a which is bigger b which has a larger input force c which has a larger output force d which makes work easier

d which makes work easier