How Things Work (Bloomfield)
Chapter 1 Test Problems for 4th ed.
Secti on 1.1 – Skati ng
1. Suppose you have two cars, and the larger one is twice as massive as the smaller one. If
you and a friend push on them so that their accelerations are equal, how must the forces
applied to the cars compare?
A) The force on the larger car is equal to that on the smaller car
B) The force on the larger car is ½ that on the smaller car.
C) The force on the larger car is twice that on the smaller car.
D) The force on the larger car is more than three times that on the smaller car.
ANS: C DIFF: E
2. Which of the following devices on a car can be used to cause the car to accelerate?
A) The gas pedal
B) The brake pedal
C) The steering wheel
D) All the above
ANS: D DIFF: E
3. The acceleration of an object is equal to
A) the rate of change of its position
B) the rate of change of its velocity
C) the rate of change of its speed only
D) the time an object has been in motion
ANS: B DIFF: E
,4. Suppose you are at a stop light and realize that an important antique physics textbook
sale ends in five minutes. Naturally, you start off very rapidly. To you, some papers on the
dashboard fly straight backwards. To an observer on the ground they
A) remained where they were.
B) moved forward rapidly.
C) moved backwards rapidly.
D) fell straight down.
ANS: A DIFF: E
5. The SI units of acceleration are
A) m/s
B) kgm/s2
C) m/s2
D) kg m2/s2
ANS: C DIFF: E
6. Suppose you have a car traveling down the road at constant speed and not changing
direction. It is experiencing gravity, wind resistance and frictional forces from the road.
What can be said about the car’s acceleration?
A) It is accelerating because there are forces acting on it.
B) It accelerating because the motor is running, propelling the car forward.
C) It is not accelerating because gravity holds it down.
D) It is not accelerating because it has constant velocity.
ANS: D DIFF: M
,7. Suppose you are driving north and suddenly hit your brakes to avoid a dog in the road. As
you come to a stop your acceleration is directed
A) North
B) South
C) Nowhere because acceleration is a scalar
D) Downwards
ANS: B DIFF: M
8. If you are backing up but slowing down, your acceleration is directed
A) backwards
B) nowhere
C) forwards
D) to the left
ANS: C DIFF: M
9. Under what conditions are the values of average speed and the magnitude of the average
velocity equal?
A) When moving in a straight line
B) When moving in a straight line and not turning around
C) When moving in a circular path
D) When walking around the perimeter of a rectangle
ANS: B DIFF: M
10. You are making a round trip from City A to City B and back to City A again at constant
speed. At what point in the trip is your average speed equal to three times the magnitude of
your average velocity?
ANS: Since velocity = change in position divided by time interval and average speed
= total distance divided by time interval we need to find a point in the trip where the
distance traveled is equal to three times the object’s change in position. Here it is useful to
, break the trip into four equal parts. We can see that halfway between the two cities on the
way back to city A, three parts distance have been covered but the difference in position is
only one part. Hence it is at the midway point on the return where the average speed is
three times the average velocity.
DIFF: H
11. A frequent flyer is suing an airline. She claims that during landing, the plane’s rapid
acceleration caused a suitcase on a luggage rack in front of her to fly backwards and hit her.
Using any of Newton’s laws of motion, please support or refute the passenger’s claim.
ANS: Here I would use Newton’s first law of motion. The plane is accelerating
backwards when landing. The book indeed has inertia, so Newton’s first law suggests that
the book would tend to remain in a constant state of motion, so it would tend to slip
forward (relative to the plane), not backward. Hence the passenger’s claim is refuted. DIFF:
M
12. A friend states Newton’s First Law of Motion as “An object will move in a straight line
unless acted upon by a force” Please evaluate the scientific merit of his statement.
ANS: the friend is almost right but has left out some very important loopholes. First
off, it is a non-zero net force that causes acceleration, not necessarily any lone force. Also, a
non-zero net force will make an object accelerate, meaning it will speed up, slow down or
curve – not just curve as the friend suggests. The object could accelerate in a straight line.
DIFF: H
13. You walk in a given direction for 20 m during the first 5 seconds of a trip and then 15 m
during the next 2 seconds. Your average speed is equal to
A) 8 m/s
B) 2 m/s
C) 5 m/s
D) –5 m/s
ANS: C DIFF: M
Chapter 1 Test Problems for 4th ed.
Secti on 1.1 – Skati ng
1. Suppose you have two cars, and the larger one is twice as massive as the smaller one. If
you and a friend push on them so that their accelerations are equal, how must the forces
applied to the cars compare?
A) The force on the larger car is equal to that on the smaller car
B) The force on the larger car is ½ that on the smaller car.
C) The force on the larger car is twice that on the smaller car.
D) The force on the larger car is more than three times that on the smaller car.
ANS: C DIFF: E
2. Which of the following devices on a car can be used to cause the car to accelerate?
A) The gas pedal
B) The brake pedal
C) The steering wheel
D) All the above
ANS: D DIFF: E
3. The acceleration of an object is equal to
A) the rate of change of its position
B) the rate of change of its velocity
C) the rate of change of its speed only
D) the time an object has been in motion
ANS: B DIFF: E
,4. Suppose you are at a stop light and realize that an important antique physics textbook
sale ends in five minutes. Naturally, you start off very rapidly. To you, some papers on the
dashboard fly straight backwards. To an observer on the ground they
A) remained where they were.
B) moved forward rapidly.
C) moved backwards rapidly.
D) fell straight down.
ANS: A DIFF: E
5. The SI units of acceleration are
A) m/s
B) kgm/s2
C) m/s2
D) kg m2/s2
ANS: C DIFF: E
6. Suppose you have a car traveling down the road at constant speed and not changing
direction. It is experiencing gravity, wind resistance and frictional forces from the road.
What can be said about the car’s acceleration?
A) It is accelerating because there are forces acting on it.
B) It accelerating because the motor is running, propelling the car forward.
C) It is not accelerating because gravity holds it down.
D) It is not accelerating because it has constant velocity.
ANS: D DIFF: M
,7. Suppose you are driving north and suddenly hit your brakes to avoid a dog in the road. As
you come to a stop your acceleration is directed
A) North
B) South
C) Nowhere because acceleration is a scalar
D) Downwards
ANS: B DIFF: M
8. If you are backing up but slowing down, your acceleration is directed
A) backwards
B) nowhere
C) forwards
D) to the left
ANS: C DIFF: M
9. Under what conditions are the values of average speed and the magnitude of the average
velocity equal?
A) When moving in a straight line
B) When moving in a straight line and not turning around
C) When moving in a circular path
D) When walking around the perimeter of a rectangle
ANS: B DIFF: M
10. You are making a round trip from City A to City B and back to City A again at constant
speed. At what point in the trip is your average speed equal to three times the magnitude of
your average velocity?
ANS: Since velocity = change in position divided by time interval and average speed
= total distance divided by time interval we need to find a point in the trip where the
distance traveled is equal to three times the object’s change in position. Here it is useful to
, break the trip into four equal parts. We can see that halfway between the two cities on the
way back to city A, three parts distance have been covered but the difference in position is
only one part. Hence it is at the midway point on the return where the average speed is
three times the average velocity.
DIFF: H
11. A frequent flyer is suing an airline. She claims that during landing, the plane’s rapid
acceleration caused a suitcase on a luggage rack in front of her to fly backwards and hit her.
Using any of Newton’s laws of motion, please support or refute the passenger’s claim.
ANS: Here I would use Newton’s first law of motion. The plane is accelerating
backwards when landing. The book indeed has inertia, so Newton’s first law suggests that
the book would tend to remain in a constant state of motion, so it would tend to slip
forward (relative to the plane), not backward. Hence the passenger’s claim is refuted. DIFF:
M
12. A friend states Newton’s First Law of Motion as “An object will move in a straight line
unless acted upon by a force” Please evaluate the scientific merit of his statement.
ANS: the friend is almost right but has left out some very important loopholes. First
off, it is a non-zero net force that causes acceleration, not necessarily any lone force. Also, a
non-zero net force will make an object accelerate, meaning it will speed up, slow down or
curve – not just curve as the friend suggests. The object could accelerate in a straight line.
DIFF: H
13. You walk in a given direction for 20 m during the first 5 seconds of a trip and then 15 m
during the next 2 seconds. Your average speed is equal to
A) 8 m/s
B) 2 m/s
C) 5 m/s
D) –5 m/s
ANS: C DIFF: M
