Physics Chapter 4

10. If a person has a mass of 60 kg on Earth, what would be their mass on the Moon? a. 60 kg b. 30 kg c. 115 kg d. 90 kg

A

12. A 72 kg person is standing on a bathroom scale (calibrated in newtons) in the middle of an elevator. What is the reading on the scale when the elevator is accelerating upward at a rate of 1.6 m/s2? a. 820 N b. 760 N c. 800 N d. 740 N

A

19. Which type of friction depends on the surface area of an object? a. air resistance b. surface kinetic friction c. surface static friction d. rolling friction

A

45. Which of the following is designed to increase friction? a. golf club grips b. fluid bearings c. near-frictionless carbon d. ice skates

A

6. Which of the following is a measure of the force of gravity acting on an object? a. weight b. mass c. inertia d. volume

A

15. A person drops a 22 kg box on a scale which for a short time reads 255 N. Determine the acceleration of the box as it hits the scale. a. 2.4 m/s2 b. 1.8 m/s2 c. 2.2 m/s2 d. 2.0 m/s2

B

25. In which of the following situations would you want to minimize friction? a. creating brakes for a bicycle b. playing ice hockey c. designing the grip for a weightlifting device d. designing track running shoes

B

41. Hydroplaning occurs when which of the following happens? a. Water builds up over ice, which reduces the amount of friction. b. Excess water builds up under the tires of a car, causing it to lose traction. c. The force of water acting on a surface causes it to break. d. A surface has the required amount of area in order to use the current of water for motion.

B

5. On average, what is the gravitational field strength on the surface of Earth? a. 9.8 N/m2 [up] b. 9.8 N/kg [down] c. 9.8 N/kg [up] d. 9.8 N/m2 [down]

B

1. Which of the following forces balances gravity for falling objects? a. tension b. electromagnetic force c. air resistance d. strong force

C

13. A 69 kg person is standing on a bathroom scale (calibrated in newtons) in the middle of an elevator. Determine the reading on the scale when the elevator is moving downward at a constant rate of 2.2 m/s. a. 520 N b. 480 N c. 680 N d. 720 N

C

14. A 15 kg box sits on top of a 24 kg box in the middle of an elevator. Calculate the normal force acting on the bottom box from the floor when the elevator is accelerating downward at a rate of 2.2 m/s2 . a. 2.2 N b. 3.8 N c. 3.0 N d. 4.7 N

C

17. What type of friction does a plane experience when in flight? a. rolling friction b. static friction c. air resistance d. none of the above

C

39. For which of the following items will the friction increase with an increasing surface area? a. wooden sleds b. steel skates c. tires d. plastic skis

C

40. What do the treads on tires do? a. Reduce the amount of rubber used when making tires. b. Help the shock absorbers absorb impact for the car. c. Provide pathways for water and snow to travel as the tire rolls. d. Increase the amount of surface area in contact with the road.

C

44. What are crumple zones in cars designed for? a. allowing the car to be scrapped and recycled easily b. changing the direction of the car during impact c. increasing the time it takes for a car to stop during a crash d. absorbing the shock from bumpy roads

C

9. Which of the following is correctly measured with a balance? a. density b. weight c. mass d. volume

C

16. In which of the following situations is a large amount of friction necessary? a. on top of an air hockey table b. on the bottom of a downhill skier's skis c. within the engine of a car d. when a car is starting to move

D

18. The force of surface friction acting on an object depends on which of the following? a. the colour of the object b. the surface area of the object c. the shape of the object d. the mass of the object

D

2. Which of the following will experience the largest amount of air resistance? a. a piece of paper rolled into a tube b. a crumpled piece of paper c. a piece of paper folded into a thin sliver d. the broad side of a flat piece of paper

D

20. Why can determining the coefficient of friction between a pair of materials be difficult? a. The materials may vary in roughness. b. The materials may not be clean. c. The materials may change in wetness. d. all of the above

D

42. With an antilock braking system, what is one thing that you should never do? a. check your brake fluid b. press the brake pedal too hard c. steer the car in the correct direction d. pump the brakes

D

43. What does traction control do? a. adjusts the pressure in the tires of a car to fit the road b. steers the car in the correct direction of the road c. slows the car down when going to fast to maintain stability d. helps the driver maintain control of the car while accelerating

D

7. Which of the following will change the mass of an object? a. placing the object in a vacuum b. changing the location c. changing the gravitational field strength d. none of the above

D

8. Which of the following will change the weight of an object? a. increasing the objects mass b. increasing the gravitational field strength c. decreasing the objects mass d. all of the above

D

Weight should be measured with a balance.

Spring scale Force Sensor

Kinetic friction is the force from contact between two surfaces acting on a stationary object.

Static Friction

The gravitational field strength of Earth is weaker at the poles than it is at the equator.

Stronger

Resultant velocity is the maximum constant speed reached by a falling object.

Terminal Velocity

1. Air resistance is friction caused by the air.

True

As an object moves away from the surface of Earth, the gravitational field strength decreases.

True

For dry weather conditions, flat tires provide more friction between the tire and road than tires with tread.

True

On the Moon or a planet other than Earth, your weight is different but your mass is the same.

True

The gravitational field strength at a location has the same magnitude as the acceleration due to gravity at that location.

True

The only way to change the mass of an object is to either add or remove matter.

True

Gravitational field strength is a scalar.

Vector

Weight is a scalar.

Vector

For each of the following locations, determine whether the gravitational field strength of Earth will be greater than or less than 9.8 N/kg. Answers may be used more than once. a. greater than b. less than ____ 10. at the poles

a

For each of the following locations, determine whether the gravitational field strength of Earth will be greater than or less than 9.8 N/kg. Answers may be used more than once. a. greater than b. less than ____ 9. in death valley 80 m below sea level

a

State whether each performed action will increase the amount of friction, decrease the amount of friction, or will have an undetermined effect. Answers may be used more than once. a. increase the amount of friction b. decrease the amount of friction c. undetermined ____ 1. using sandpaper to rough up the bottom of a sled

a

State whether each performed action will increase the amount of friction, decrease the amount of friction, or will have an undetermined effect. Answers may be used more than once. a. increase the amount of friction b. decrease the amount of friction c. undetermined ____ 5. adding a weight to a ball that is dropped to the ground

a

15. ____________________ are deployed during a car accident to help prevent the people inside a car from hitting a hard surface like the dashboard or steering wheel.

airbags

12. ____________________ is a system designed to prevent brake pads on cars from maintaining contact with the wheel hub, and instead forces them to pulse rapidly.

anti lock braking

11. What fraction is the strength of the Moon's gravitational field compared to Earth's? a. 1/4 b. 1/6 c. 1/8 d. 1/12

b

For each of the following locations, determine whether the gravitational field strength of Earth will be greater than or less than 9.8 N/kg. Answers may be used more than once. a. greater than b. less than ____ 7. at the equator

b

For each of the following locations, determine whether the gravitational field strength of Earth will be greater than or less than 9.8 N/kg. Answers may be used more than once. a. greater than b. less than ____ 11. on top of Mt. Everest

b

For each of the following locations, determine whether the gravitational field strength of Earth will be greater than or less than 9.8 N/kg. Answers may be used more than once. a. greater than b. less than ____ 8. astronauts in orbit at 1 Earth radius

b

State whether each performed action will increase the amount of friction, decrease the amount of friction, or will have an undetermined effect. Answers may be used more than once. a. increase the amount of friction b. decrease the amount of friction c. undetermined ____ 2. adding lubricant to an engine

b

State whether each performed action will increase the amount of friction, decrease the amount of friction, or will have an undetermined effect. Answers may be used more than once. a. increase the amount of friction b. decrease the amount of friction c. undetermined ____ 6. cleaning the floor before pushing a box across it

b

State whether each performed action will increase the amount of friction, decrease the amount of friction, or will have an undetermined effect. Answers may be used more than once. a. increase the amount of friction b. decrease the amount of friction c. undetermined ____ 3. unfolding a paper airplane into a flat sheet of paper and throwing it through the air.

c

State whether each performed action will increase the amount of friction, decrease the amount of friction, or will have an undetermined effect. Answers may be used more than once. a. increase the amount of friction b. decrease the amount of friction c. undetermined ____ 4. rain falling on a road

c

2. Air resistance depends on the ____________________ of an object.

cross-sectional area

14. ____________________ are regions in cars that are designed to maximize the time interval during a car collision.

crumple zones

3. Slower moving objects experience more air resistance.

faster

Rubber bearings are devices that contain a liquid and are used to reduce friction in rotating parts.

fluid

9. The friction involved with boats moving through water is known as ____________________.

fluid friction

4. A(n) ____________________ is a region of space surrounding an object that can exert a force on other objects placed within that region.

forcefield

1. When an object is falling under the influence of gravity only, the object is said to be in ____________________.

free fall

5. ____________________ is the force per unit mass acting on an object when placed in a gravitational field.

gravitational field strength

Brake pads that pulse rapidly on and off the wheel hub will slow down a car at a lower rate than if the pads held firmly.

higher

13. ____________________ occurs when the traction is poor on a tire and the wheels lose contact with the road in wet conditions.

hydroplaning

Crumple zones are designed to decrease the distance a car will travel in a head on collision.

increase

Running shoes are typically designed to reduce the amount of friction between the sole and the floor of the ground.

increase

Opening a parachute slows down a skydiver by decreasing the gravitational field.

increasing the cross-sectional area

When two surfaces are in contact with one another, the amount of friction between them depends on the surface area.

is independent of

10. ____________________ are a type of bearing that keep two surfaces completely out of contact by levitation.

magnetic bearings

6. ____________________ is the quantity of matter in an object.

mass

2. Larger cross-sectional areas experience less air resistance than smaller cross- sectional areas.

more

A round object rolling across a surface will experience fluid friction.

rolling friction

11. Golf clubs are designed with ____________________ handles to increase the amount of friction between the golfers grip and the club.

rubber

The coefficient of friction is a vector.

scalar

8. ____________________ is the force exerted on a stationary object by a surface that prevents the object from starting to move.

static friction

7. In the joints of the human body, ____________________ helps reduce friction between moving bones.

synovial fluid

3. The maximum constant speed reached by a falling object is called the ____________________.

terminal velocity

When you are pulling or pushing a stationary object, it will start to move after the force of kinetic friction is reached.

the maximum force of static friction

The gravitational field of Earth always points normal to the surface, even on a slope.

toward earth's centre

A thin layer of slushy water exists on ice rinks that reduces friction between the ice and skate.

true

Air resistance acts in the opposite direction of motion if there is no wind.

true

Increasing the speed of an object will increase the air resistance acting on it.

true

The coefficient of friction is the ratio of the magnitude of the force of friction acting on an object to the magnitude of the normal force acting on the object.

true

When pushing or pulling two or more attached objects, you must overcome the combined force of friction acting on both.

true

The coefficients of friction between an object and a surface depend only on the mass of the object.

type of materials