Conceptual Physics Chapter 3

A cart changes its speed from 90 m/s to 100 m/s in 10 seconds. During this interval its acceleration is

1 m/s^2

The time it takes a car to attain a speed of 30 m/s when accelerating from rest at 2 m/s2 is

15 s

C

15) If a rocket initially at rest accelerates at a rate of 50 m/s2 for one minute, its speed will be A) 50 m/s. B) 500 m/s. C) 3000 m/s. D) 3600 m/s. E) none of these.

A car's speed 3 seconds after accelerating from rest at 2 m/s2 is

6 m/s.

If a car increases its velocity from zero to 60 m/s in 10 seconds, its acceleration is

6 m/s^2

At one instant an object in free fall is moving downward at 50 m/s. One second later its speed is

60 m/s.

A

7) As an object freely falls downward, its A) velocity increases. B) acceleration increases. C) both of these. D) none of these.

An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration is

0 m/s^2

A vehicle undergoes acceleration when it

1) Changes its direction 2) Gains speed 3) Loses speed (ALL OF THE ABOVE)

If a freely falling object were equipped with a speedometer, its speed reading would increase each second by about

10 m/s.

If you throw a ball straight downward (in the absence of air resistance), after leaving your hand its acceleration is

10 m/s^2

Neglecting air resistance, a bullet fired straight down from the top of a high cliff has an acceleration of

10 m/s^2

When a ball thrown straight upwards reaches the very top of its path, its acceleration is

10 m/s^2

D

19) A car accelerates from rest at 2 meters per second per second. What is its speed 3 seconds after the car starts moving? A) 2 m/s B) 3 m/s C) 4 m/s D) 6 m/s E) none of these

A ball starting from rest at the top of an inclined plane gains a speed of 2 m/s for each second it rolls. What is its acceleration down the incline?

2 m/s^2

The total time it takes a projectile fired straight up at 10 m/s to reach the top of its path and return to its starting point is about

2 s

B

2) Which of the following is not a vector quantity? A) velocity B) speed C) acceleration D) None are vector quantities. E) All are vector quantities.

When you walk at an average speed of 4 m/s, in 5 s you'll cover a distance of

20 m

If a freely falling object were equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s2, then its speed reading would increase each second by

20 m/s.

If an object moves with constant acceleration, its velocity must

change by the same amount each second.

A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always

directed downward.

The difference between speed and velocity involves

direction.

A ball rolling down an inclined plane each second picks up

the same amount of speed each second.

A ball is thrown upwards and returns to the same location. Compared with its initial speed its speed when it returns is about

the same.

A rock dropped from a 5-m height accelerates at 10 m/s2 and strikes the ground 1 s later. If the rock is dropped from a height of 2.5 m, its acceleration of fall is

the same.

A

1) Galileo's use of inclined planes allowed him to effectively A) slow down the acceleration of free fall. B) increase the acceleration beyond that of free fall. C) eliminate the acceleration of free fall. D) all of these. E) none of these.

While a car travels around a circular track at a constant speed, its

1) Inertia is zero 2) Velocity is zero 3) Acceleration is zero (NONE OF THE ABOVE)

What is the acceleration of a car moving along a straight road that increases its speed from 0 to 100 km/h in 10 s?

10 km/h·s

B

16) Drop a rock from a 5-m height and it accelerates at 10 m/s2 and strikes the ground 1 s later. Drop the same rock from a height of 2.5 m and its acceleration of fall is A) about half. B) the same. C) more.

E

28) An object falls freely from rest on a planet where the acceleration due to gravity is 20 meters per second squared. After 5 seconds, the object will have a speed of A) 5 m/s. B) 10 m/s. C) 20 m/s. D) 50 m/s. E) 100 m/s.

C

29) An object falls freely from rest on a planet where the acceleration due to gravity is 20 meters per second squared. In the first 5 seconds it falls a distance of A) 100 m. B) 150 m. C) 250 m. D) 500 m. E) none of these.

A

3) An airplane that flies at 100 km/h with a 10 km/h tailwind travels at 110 km/h relative to the ground. If it instead flies into a 10 km/h headwind, its groundspeed is A) 90 km/h. B) 100 km/h. C) 110 km/h. D) 120 km/h.

What is the average speed in kilometers per hour of a horse that gallops a distance of 15 km in a time of 30 min?

30 km/h

B

30) An apple falls from a tree and hits the ground 5 meters below. It hits the ground with a speed of about A) 5 m/s. B) 10 m/s. C) 15 m/s. D) 20 m/s. E) not enough information given to estimate.

C

31) It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft? A) about 60 m B) about 120 m C) about 180 m D) more than 200 m

B

32) If you drop an object, it will accelerate downward at a rate of 9.8 meters per second per second. If you instead throw it downwards, its acceleration (in the absence of air resistance) will be A) less than 9.8 meters per second per second. B) 9.8 meters per second per second. C) greater than 9.8 meters per second per second.

D

33) In each second of fall, the distance a freely falling object will fall is A) about 5 m. B) about 10 m. C) the same, but not 5 m or 10 m. D) increasing. E) none of these.

A

34) If a projectile is fired straight up at a speed of 10 m/s, the time it takes to reach the top of its path is about A) 1 second B) 2 seconds C) 10 seconds D) not enough information to estimate

B

35) If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting position is about A) 1 second. B) 2 seconds. C) 10 seconds. D) 20 seconds. E) not enough information to estimate.

B

38) A car accelerates at 2 meters per second per second. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 30 m/s? A) 2 seconds B) 15 seconds C) 30 seconds D) 60 seconds E) none of these

D

39) A car accelerates from rest for 5 seconds until it reaches a speed of 20 m/s. What is the car's acceleration in meters per second per second? A) 1 B) 2 C) 3 D) 4 E) 5

What is the acceleration of a car that starts from rest and 5 seconds later reaches a speed of 20 m/s?

4 m/s^2

C

4) The two measurements necessary for calculating average speed are A) acceleration and time. B) velocity and time. C) distance and time. D) distance and acceleration. E) velocity and distance.

At one instant a heavy object in air is moving upward at 50 m/s. One second later its speed is approximately

40 m/s

C

40) Ten seconds after starting from rest, a car is moving at 40 m/s. What is the car's acceleration in meters per second per second? A) 0.25 B) 2.8 C) 4.0 D) 10 E) 40

B

41) When a rock thrown straight upwards gets to the exact top of its path, its A) velocity is zero and its acceleration is zero. B) velocity is zero and its acceleration is about 10 meters per second per second. C) velocity is about 10 m/s and its acceleration is zero. D) velocity is about 10 m/s and its acceleration is about 10 meters per second per second. E) none of these.

A

47) A ball is thrown upwards. Neglecting air resistance, what initial upward speed does the ball need to remain in the air for a total time of 10 seconds? A) about 50 m/s B) about 60 m/s C) about 80 m/s D) about 100 m/s E) about 110 m/s

B

48) A ball is thrown 125 meters upward and then falls the same distance back to Earth. Neglecting air resistance, its total time in the air is about A) 5 seconds. B) 10 seconds. C) 15 seconds. D) more than 20 seconds.

A

49) A pot falls from a ledge and hits the ground 45 m below. The speed with which it hits the ground is about A) 30 m/s. B) 60 m/s. C) 120 m/s. D) more than 120 m/s.

In its first second of free fall, a dropped softball will fall a vertical distance of

5 m

B

5) The average speed of a horse that gallops a distance of 10 kilometers in a time of 30 minutes is A) 10 km/h. B) 20 km/h. C) 30 km/h. D) more than 30 km/h.

C

50) The vertical height attained by a basketball player who achieves a hang time of a full 1 s is about A) 0.8 m. B) 1 m. C) 1.2 m. D) 2.5 m. E) more than 2.5 m.

B

51) A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. Neglecting air resistance, one second later the rock's speed is A) zero. B) 4.9 m/s. C) 9.8 m/s. D) 14.7 m/s. E) none of the above.

D

52) A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. Neglecting air resistance, two seconds later the rock's speed is A) zero. B) 4.9 m/s. C) 9.8 m/s. D) 14.7 m/s. E) none of the above.

A

8) A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is A) zero newtons. B) equal to the weight of the puck. C) the weight of the puck divided by the mass of the puck. D) the mass of the puck multiplied by 9.8 meters per second per second. E) none of these.

What is the effect of air resistance on the acceleration of falling objects?

Air resistance decreases the acceleration of falling objects.

Which BEST describes what occurs when a body accelerates?

Change in velocity per unit time.

Why does the distance traveled by the ball in each half second after it is released change in the way that it does?

Gravity is pulling down on the ball, so it accelerates down at a steady rate.

What is the gain in speed per second for a freely falling object?

It gains approximately 10 m/s.

As the angle of the inclined plane increases, how does the final speed attained by the ball at the bottom of the inclined plane change?

It increases.

How does the acceleration of the ball change as the angle of the inclined plane increases?

It increases.

How does the distance traveled by the ball in the second half second compare with the distance traveled by the ball in the first half second?

It increases.

Phil Physiker standing at the edge of a cliff throws one ball straight up and another ball straight down, both with the same speed. Neglecting air resistance, which ball hits the ground below with the greater speed?

Neither, both hit with the same speed.

Why does the final speed attained by the ball at the bottom of the inclined plane change in the way that it does when the angle of the incline plane increases?

The ball accelerates at a greater rate for the same duration of time.

If a car moves with a constant velocity, does it also move with a constant speed?

Yes, because constant velocity requires constant speed in the same direction.

Galileo discovered that when air resistance can be neglected, all objects fall with the same

acceleration.

When we are talking about how quickly "how fast" changes, we're talking about

acceleration.

A speedometer normally measures

instantaneous speed.

C

10) If an object falling freely downward were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be A) constant. B) less and less. C) greater than the second before.

C

11) Ten seconds after starting from rest, an object falling freely downward will have a speed of about A) 10 m/s. B) 50 m/s. C) 100 m/s. D) more than 100 m/s.

B

12) If an object falls with constant acceleration, the velocity of the object must A) be constant also. B) continuously change by the same amount each second. C) continuously change by varying amounts depending on its speed. D) continuously decrease. E) none of these.

B

13) A heavy object and a light object are dropped at the same time from rest in a vacuum. The heavier object reaches the ground A) sooner than the lighter object. B) at the same time as the lighter object. C) later than the lighter object.

B

14) If a car increases its velocity from zero to 60 km/h in 10 seconds, its acceleration is A) 3 km/h s. B) 6 km/h s. C) 10 km/h s. D) 60 km/h s. E) 600 km/h s.

What is the speed over the ground of an airplane flying at 100 km/h relative to the air caught in a 100-km/h right-angle crosswind?

141 km/h

D

17) A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always A) in the direction of motion. B) opposite its velocity. C) directed upward. D) directed downward.

D

18) While a car travels around a circular track at constant speed its A) acceleration is zero. B) velocity is zero. C) both of these. D) none of these.

If a stone falls to the bottom of a mineshaft in 6 seconds, then the depth of the shaft is about

180 m

C

20) A ball is thrown upwards and caught when it comes back down. Neglecting air resistance, its speed when caught is A) more than the speed it had when thrown upwards. B) less than the speed it had when thrown upwards. C) the same as the speed it had when thrown upwards.

A

21) An object travels 8 meters in the first second of travel, 8 meters again during the second second of travel, and 8 meters again during the third second. Its acceleration in meters per second per second is A) 0. B) 5. C) 8. D) 10. E) more than 10.

D

22) At one instant an object in free fall is moving downward at 50 meters per second. One second later its speed is about A) 25 m/s. B) 50 m/s. C) 55 m/s. D) 60 m/s. E) 100 m/s.

E

23) At one instant an object in free fall is moving upward at 50 meters per second. One second later its speed is about A) 100 m/s. B) 60 m/s. C) 55 m/s. D) 50 m/s. E) 40 m/s.

C

24) Disregarding air resistance, objects fall with constant A) velocity. B) speed. C) acceleration. D) distances each successive second.

B

25) A ball is thrown upwards and caught when it comes back down. In the presence of air resistance, the speed with which it is caught is A) more than the speed it had when thrown upwards. B) less than the speed it had when thrown upwards. C) the same as the speed it had when thrown upwards.

C

26) Starting from rest, the distance a freely-falling object will fall in 0.5 seconds is about A) 0.5 m. B) 1.0 m. C) 1.25 m. D) 5.0 m. E) none of these.

C

27) One half second after starting from rest, a freely-falling object will have a speed of about A) 20 m/s. B) 10 m/s. C) 5 m/s. D) 2.5 m/s. E) none of these.

B

36) Consider drops of water that leak from a dripping faucet. As the drops fall they A) get closer together. B) get farther apart. C) remain at a relatively fixed distance from one another.

C

37) Disregarding air drag, how fast must you toss a ball straight up in order for it to take 2 seconds to return to the level from which you tossed it? A) 5 m/s B) 7.5 m/s C) 10 m/s D) 15 m/s E) 20 m/s

C

42) A bullet is dropped from the top of the Empire State Building while another bullet is fired downward from the same location. Neglecting air resistance, the acceleration of A) the fired bullet is greater. B) the dropped bullet is greater. C) each bullet is 9.8 meters per second per second.

A

43) The muzzle velocity of a certain gun is 100 m/s. Neglecting air resistance, at the end of one second a bullet fired straight up into the air will have traveled a distance of A) (100 - 4.9) m. B) (100 + 4.9) m. C) 100 m. D) 4.9 m. E) none of these.

B

44) A bullet is fired straight down from the top of a high cliff. Neglecting air resistance, the acceleration of the bullet in meters per second per second is A) less than 9.8. B) 9.8. C) more than 9.8.

C

45) A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun, straight down towards the water. Neglecting air resistance, the acceleration just before striking the water A) is greater for the dropped bullet. B) is greater for the fired bullet. C) is the same for each bullet. D) depends on how high they started. E) none of these.

C

46) Someone standing at the edge of a cliff throws one ball straight up and another ball straight down at the same initial speed. Neglecting air resistance, the ball to hit the ground below the cliff with the greater speed will be A) the one thrown upward. B) the one thrown downward. C) neither - they will both hit with the same speed.

B

53) A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. How far below the level from which it was thrown is the rock 2 seconds later? A) 4.9 m B) 9.8 m C) 14.7 m D) 19.6 m

Jogging Jake runs at 4 m/s along a train flatcar that moves at 10 m/s in the opposite direction. Jake's speed relative to the ground is

6 m/s

A

6) What is the acceleration of a car that maintains a constant velocity of 100 km/hr for 10 seconds? A) 0 B) 10 km/hr s C) 10 m/hr s D) 1000 km/hr s

D

9) If an object falling freely downward were somehow equipped with a speedometer on a planet where the acceleration due to gravity is 40 meters per second per second, then its speed reading would increase each second by A) 10 m/s. B) 20 m/s. C) 30 m/s. D) 40 m/s. E) depends on its initial speed.

What exactly is meant by a "freely falling" object?

An object in free fall falls under gravity alone with no friction.

You are not moving relative to the chair, but you are moving over 100,000 km/h relative to the Sun.

As you read this in your chair, how fast are you moving relative to the chair? Relative to the Sun?

How can you use the graph of velocity versus time to estimate the acceleration of the ball?

By estimating the value of the slope of the graph.

If a car is moving at 90 km/h and it rounds a corner, also at 90 km/h, does it maintain a constant speed? A constant velocity? If a car is moving at 90 km/h and it rounds a corner, also at 90 km/h, does it maintain a constant speed? A constant velocity?

It maintains a constant speed, but does not maintain a constant velocity.