Conceptual Physics Chapter 3

Calculate your walking speed when you step 1.0 meter in 0.55 second.

1.8 m/s

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

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

10 m/s.

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

10 m/s^2

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.

A car accelerates at 2 meters/s/s. Assuming the car starts from rest, how far will it travel in 10 s?

100 m

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

100 m/s.

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.

While you're in a bus that moves at 100 km/h, you walk from the back to the front at 10 km/h. What is your speed relative to the road outside?

110 km/h

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.

An apple drops from a tree and hits the ground in 1.6s . Calculate how far it falls.

13 m

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.

vector quantity

a quantity that has magnitude and direction

scalar quantity

a quantity that has only a magnitude, not a direction

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.

instantaneous speed

the speed at any instant

average speed

the total distance traveled divided by the time of travel

The difference between speed and velocity involves _______.

direction

The difference between speed and velocity involves

direction.

A mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the opposite direction has a speed of

0 m/s

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

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 in meters per second per second is approximately

0.

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

20 m

An object at rest near the surface of a distant planet starts to fall freely. If the acceleration there is twice that of the Earth, its speed one second later would be

20 m/s

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.

C

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

Calculate the average speed of a cheetah that runs 150 meters in 6.0 seconds.

25 m/s

An object falls freely from rest on a planet where the acceleration due to gravity is twice as much as on Earth. In the first 5 seconds it falls a distance of

250 m

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.

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.

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

At one instant a heavy object in air is moving upward at 50 meters per second. 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

An object is dropped from rest and falls freely. After 7.8s , calculate its instantaneous speed.

78 ms

Calculate the distance (in km) that Larry runs if he maintains an average speed of 9.3km/h for 1 hour.

9.3 km

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

9.8 meters per second per second.

Calculate the vertical distance an object dropped from rest covers in 14s of free fall.

980 m

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 instantaneous velocity of a freely falling object 14s after it is released from a position of rest?

140 m/s

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.

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.

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

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

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

2 seconds.

A horse gallops a distance of 10 kilometers in a time of 30 minutes. Its average speed is

20 km/h

The average speed of a horse that gallops 10 kilometers in 30 minutes is

20 km/h

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

A ball freely falling at 20 m/s will in the next second have a speed of _______.

30 m/s

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

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

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

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

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.

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

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.

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.

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

A mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the same direction has a speed of

6 m/s

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

6 m/s.

If a car accelerates from rest at 2 meters per second per second, its speed 3 seconds later will be about

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

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

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

60 m/s.

What is its average velocity during this 14-s interval?

69 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.

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

Air resistance decreases the acceleration of falling objects.

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

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

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.

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.

If an object falling freely were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be

Greater than the second before.

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

It gains approximately 10 m/s.

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

It increases.

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.

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.

It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?

about 180 m

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

acceleration.

velocity

an object's speed and direction of motion

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.

If an object moves with constant acceleration, its velocity must

change by the same amount each second.

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

each bullet is 9.8 meters per second per second.

speed

how fast an object moves; the distance traveled per unit of time

In each second of fall, the distance a freely falling object will fall is

increasing.

free fall

motion under the influence of gravity only

While an iron block near the Earth's surface is in free fall, it undergoes an increase in

speed.

acceleration

the rate at which velocity changes with time; the change in velocity may be in magnitude, or direction or both

A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval its acceleration is

zero.

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

zero.