Physics 011

Chapter 2

Answers of MC#2A

 

 

1.

 

A bird flies 4.0 meters due north in 2.0 seconds and then flies 2.0 meters due west in 1.0 seconds. What is the bird's average speed?
The correct answer: 2.0 m/s

 

 

2.

 

If a car is travelling due south with a decreasing speed, then the direction of the car's acceleration is
The correct answer: due north.

 

 

3.

 

A hiker travels 60 meters north and then 120 meters south. What is her resultant displacement?
 The correct answer: 60 m south

See Section 2-1

 

 

4.

 

If the average speed of a plane is 500 km per hour, how long will it take to fly 125 km?
 The correct answer: 0.25 h

See Section 2-2

 

 

5.

 

Applying the brakes to a car traveling at 45 km/h provides an acceleration of 5.0 m/s2 in the opposite direction. How long will it take the car to stop?
 The correct answer: 2.5 s

See Section 2-5

 

 

6.

 

A ball rolls down a frictionless inclined plane with a uniform acceleration of 1.0 m/s2. If its velocity at some instant of time is 10 m/s, what will be its velocity 5.0 seconds later?
 The correct answer: 15 m/s

See Section 2-5

 

 

7.

 

A ball rolls down a frictionless inclined plane with a uniform acceleration of 1.0 m/s2. If its initial velocity is 1.00 m/s, how far will it travel in 10 s?
 The correct answer: 60 m

See Section 2-5

 

 

8.

 

A body with an initial speed of 25 m/s accelerates uniformly for 10 seconds to a final speed of 75 m/s. What is the acceleration?
The correct answer: 5 m/s2

 

 

9.

 

A body initially at rest is accelerated at 5 m/s2 for 10 seconds. What is its final velocity?
 The correct answer: 50 m/s

See Section 2-5

 

 

10.

 

Which graph represents the motion of a body starting from rest and moving with a constant non-zero acceleration?
The correct answer:

 

 

11.

 

The speeds of a body at the ends of five successive seconds are: 180, 360, 540, 720, 900 m/h. What is the acceleration of the body?
 The correct answer: 0.05 m/s2

See Section 2-4

 

 

12.

 

"An object is initially at rest then moves in a straight line and accelerates uniformly at a rate of 2.00 m/s2."

After the object has been in motion for four seconds, its speed would be ___ m/s.
The correct answer: 8.0

 

 

13.

 

"An object is initially at rest then moves in a straight line and accelerates uniformly at a rate of 2.00 m/s2."

The distance traveled by the object during the first five seconds of its travel was ___ m.
The correct answer: 25

See Section 2-5

 

 

14.

 

"An object is initially at rest then moves in a straight line and accelerates uniformly at a rate of 2.00 m/s2."

The average speed of the object during the first six seconds of its travel was ___ m/s.
The correct answer: 6.0

See Section 2-5

 

 

15.

 

"An object is initially at rest then moves in a straight line and accelerates uniformly at a rate of 2.00 m/s2."

The average speed of the object during the third second of its motion was ___ m/s.
The correct answer: 5.0

 

 

16.

 

"An object is initially at rest then moves in a straight line and accelerates uniformly at a rate of 2.00 m/s2."

The distance traveled by the object during the fourth second of its travel was ___ m.
 The correct answer: 7.0

See Section 2-5

 

 

17.

 

"An object of mass m initially at rest experiences a constant acceleration of magnitude ao. After a time interval to has elapsed, the speed of the car is vo and it has traveled a distance do."

After a total time 3 to has elapsed, the speed of the object will be vox ___.
 The correct answer: 3

See Section 2-5

 

 

18.

 

"An object of mass m initially at rest experiences a constant acceleration of magnitude ao. After a time interval to has elapsed, the speed of the car is vo and it has traveled a distance do."

After a total time 2 to has elapsed, the distance traveled by the object will be dox ___.
 The correct answer: 4

See Section 2-5

 

 

19.

 

"Six different objects are observed to move in a straight line. Some aspect of the motion of each of the six objects is plotted as a function of time in the following graphs."

Which graph(s) represent(s) a situation in which the object moved with a constant nonzero acceleration?
 The correct answer:

See Section 2-8

 

 

20.

 

"Six different objects are observed to move in a straight line. Some aspect of the motion of each of the six objects is plotted as a function of time in the following graphs."

Which graph represents a situation in which the object moved with a constant zero acceleration?
 The correct answer: Graph A

See Section 2-8

 

 

21.

 

"An object is observed to move in a straight line. Some aspect of the motion of this object is plotted as a function of time in the following graph."

The slope of the dashed line in the graph above represents ___.
The correct answer: an instantaneous speed

 

 

22.

 

"An object is observed to move in a straight line. Some aspect of the motion of this object is plotted as a function of time in the following graph."

The slope of the dashed line in the graph above represents ____.
 The correct answer: an average acceleration

See Section 2-8

 

 

23.

 

"An object is observed to move in a straight line. Some aspect of the motion of this object is plotted as a function of time in the following graph."

The shaded area in the graph above represents ___.
 The correct answer: a change in position or a distance traveled

See Section 2-8

 

 

24.

 

"An object is observed to move in a straight line. Some aspect of the motion of this object is plotted as a function of time in the following graph."

The shaded area in the graph above represents ___.
 The correct answer: a distance traveled

See Section 2-8

 

 

25.

 

"The speed of an object moving in a straight line changes with time as in the figure below."

For which of the time intervals was the average speed of the object greatest?
 The correct answer: t = 2 to t = 3s

See Section 2-8

 

 

26.

 

"The speed of an object moving in a straight line changes with time as in the figure below."

During which time interval did the object travel with a constant nonzero acceleration?
 The correct answer: t = 0 to t = 1s

See Section 2-8

 

 

27.

 

"The speed of an object moving in a straight line changes with time as in the figure below."

During which time interval was the average speed least?
 The correct answer: t = 4 to t = 5s

See Section 2-8

 

 

28.

 

"The speed of an object moving in a straight line changes with time as in the figure below."

During which time interval did the maximum value of the magnitude of the instantaneous acceleration occur?
 The correct answer: t = 3 to t = 4s

See Section 2-8

 

 

29.

 

"The speed of an object moving in a straight line changes with time as in the figure below."

During which time interval was the speed of the object constant?
The correct answer: t = 4 to t = 5s

 

 

30.

 

"The speed of an object moving in a straight line changes with time as in the figure below."

During which time interval did the minimum value of the instantaneous speed occur?
The correct answer: t = 3 to t = 4s

 

 

31.

 

"The speed of an object moving in a straight line changes with time as in the figure below."

During which time interval was the magnitude of the average acceleration greatest?
The correct answer: t = 3 to t = 4s

 

 

32.

 

"The speed of an object moving in a straight line changes with time as in the figure below."

During which time interval was the magnitude of the average acceleration least?
 The correct answer: t = 4 to t = 5s

See Section 2-8

 

 

33.

 

"For this question, assume that g = 10.00 m/s2. A small stone originally at rest is dropped over the edge of a very tall building."

During the fourth second of the fall, the speed of the stone changes ___ m/s.


The correct answer: 10

 

 

34.

 

"For this question, assume that g = 10.00 m/s2. A small stone originally at rest is dropped over the edge of a very tall building."

During the second second of fall, the average speed of the stone is ___ m/s.
 The correct answer: 15

See Section 2-7 and/or 2-5

 

 

35.

 

"For this question, assume that g = 10.00 m/s2. A small stone originally at rest is dropped over the edge of a very tall building."

During the first second of fall, the stone falls a distance of ___ m.
The correct answer: 5.0

 

 

36.

 

"For this question, assume that g = 10.00 m/s2. One reaches out over the edge of a tall building and throws a stone straight up with an initial speed of 20.00 m/s."

The change in speed of the stone during the first second of its motion is ___ the change in its speed during the third second of its motion.
 The correct answer: more than

See Section 2-7 and/or 2-5

 

 

37.

 

"For this question, assume that g = 10.00 m/s2. One reaches out over the edge of a tall building and throws a stone straight up with an initial speed of 20.00 m/s."

The distance traveled by the stone during the 1st second is ___ the distance traveled by the stone during the 2nd second.
 The correct answer: more than

See Section 2-7 and/or 2-5

 

 

38.

 

"For this question, assume that g = 10.00 m/s2. One reaches out over the edge of a tall building and throws a stone straight up with an initial speed of 20.00 m/s."

At the instant the stone is at its maximum altitude, the acceleration of the stone is ___.
Your answer: something else
The correct answer: 10 m/s2 downward

See Section 2-7 and/or 2-5

 

 

39.

 

"For this question, assume that g = 10.00 m/s2. One reaches out over the edge of a tall building and throws a stone straight up with an initial speed of 20.00 m/s."

The time required for the stone to reach its maximum altitude is ___ sec.
 The correct answer: 2

See Section 2-7 and/or 2-5