Transcript Adapted from Eric Mazur`s Peer Instruction

Conceptual Physics
Concept Test Questions
Actions and Reactions
The following slides
were created through a
collaboration of the
Industry Initiatives in
Science and Math
Education (IISME) and
Stanford University
A vase of flowers is at rest on a table in a room in a building
rooted to the earth. There is no significant air movement.
The number of forces acting on
the vase is..
a. 0
b. 1
c. 2
The space shuttle is able to lift off
the ground because..
a. rocket propulsion is due to exhaust gases that push on
something behind the rocket.
b. the Earth resists the gases coming out of the back of
the rocket.
c. the gases coming out of the rocket push back on the
rocket.
d. the heat from the rocket engine causes hot air to rise,
and that rising air lifts the rocket up.
A man is pushing on box 'A'.
Which of the following is not true?
a. Box A is pushing on box B.
b. Box B is pushing on box A.
c. Box A is pushing on the man.
d. Box B is not doing any pushing.
e. b and c.
A man pushes against a wall. Besides
his force on the wall, there is a force..
a. from the wall back on the man.
b. holding the man back from behind. Otherwise, he
would knock the wall over.
c. nowhere. Only the man and maybe gravity are
exerting forces in this example.
A person pulls a box across the floor. Which is the correct
analysis of the situation?
1. The box moves forward because the person pulls forward
slightly harder on the box than the box pulls backward on the
person.
2. Because action always equals reaction, the person cannot
pull the box- the box pulls backward just as hard as the
person pulls forward, so there is no motion.
3. The person gets the box to move by giving it a tug during
which the force on the box is momentarily greater than the
force exerted by the box on the person.
4. The person’s force on the box is as strong as the force of
the box on the person, but the frictional force on the person
is forward and large while the backward frictional force on the
box is small.
5. The person can pull the box forward only if he or she
weighs more than the box.
Two men attempt to pull apart a coconut and are unable to
do so. If instead, one rope is tied to a very strong tree and
both men pull on the other end, the tension on the coconut
would be __________ what it was originally.
1. twice
2. exactly the same as
3. half
Adapted from Eric Mazur’s Peer Instruction
A horse is pulling a buggy at a
constant velocity. Which of the
following forces are acting on the
buggy?
a) The force of the horse
b) The force of the reigns
c) The force of the horse transmitted through the reins
d) All of the above
A ball, attached to a chain, is
swung in a circular pattern as
depicted to the left. Which of the
following forces provides the
centripetal acceleration necessary
for the ball to remain in a circle?
a) Gravity
b) The force on the ball by the man
c) The force on the ball by the chain
d) All of the above
A ball, attached to a chain, is
swung in a circular pattern as
depicted to the left. The removal
of which of the following forces
would cause the ball to fly off in a
straight line, as shown?
a) Gravity
b) The force on the chain by the man
c) The force on the ball by the chain
d) (a) and (b)
e) (b) and (c)
f) (a) and (c)
Consider a horse standing on the ground. Is the following
statement true?
The weight of the horse and the normal force exerted by the
ground on the horse constitute an action-reaction pair that
are always equal and opposite according to Newton’s third
law.
1. yes
2. no
Adapted from Eric Mazur’s Peer Instruction
Consider a car at rest. We can conclude that the downward
gravitational pull of Earth on the car and the upward contact
force of Earth on it are equal and opposite because ______
1. the two forces form an interaction pair.
2. the net force on the car is zero.
3. neither of the above
A skydiver is falling with a
constant velocity of 60 ms-1.
Choose the correct list of forces acting on
the skydiver.
a. Gravity down only
b. Gravity down and air pushing up
c. Gravity down and air pushing down
d. There are no forces on this skydiver.
A man is pushing to the right
on a box, but it is not moving.
Select the choice below
that correctly identifies the
forces on the box.
a. Force of man pushing to the right only.
b. Force of man pushing to the right and force of
friction to the left.
c. Force of man to the right and force of friction to the
right.
d. Force of friction only.
e. There are no forces acting on the cube.
Two identical blocks rest on two identical tables. A pig on
a pogo stick is bouncing on block B.
Compared to the normal force exerted by
the table on block A, the normal force
exerted by the table on block B is..
a. the same.
b. greater.
c. less
A girl is accelerating upward
on a diving board.
The normal force of the diving board on the girl is..
a. less than the girl's weight.
b. equal to the girl's weight.
c. more than the girl's weight.
d. zero.
A person is standing in an elevator that is accelerating
upward. The upward normal force, N, exerted by the
elevator floor on the person is ____________ the
downward weight W of the person.
1. larger than
2. identical to
3. smaller than
Acceleratin
g
Adapted from Eric Mazur’s Peer Instruction
Which of the following statements is not true.
a. The woman is pushing up on box B.
b. Box B is pushing up on box A.
c. Box A is pushing down on box B.
d. Box B is pushing down on the woman.
e. Box B is not doing any pushing.
f. b, c, and d.
Below is a list of possible forces present for the situation of
a woman sitting in a chair.
1. Woman's force on chair.
2. Chair's force on woman
3. Chair's force on ground.
4. Ground's force on woman.
5. Woman's force on ground from foot.
Which of the above are real forces?
a. none
b. all
c. 1 and 5
d. 1,4, and 5
Rockets move in space because..
a. the burning gases push on the rocket.
b. the burning gases push on whatever is behind the rocket.
c. the rocket sucks in and pushes back space gases just
like a jet turbine.
This world record land rocket moves forward because..
a. burning gases push on the ground at an angle.
b. air is sucked in the front and pushed out the back.
c. air and burning gases push forward on the rocket.
A bird at rest on a branch is facing the wind. The wind is
constant and the bird is not moving.
The number of forces acting on
the bird is..
a. 0
b. 1
c. 2
d. 3
e. at least 4
A boy is at rest on a steep hill with his foot on a skateboard.
The skateboard is not moving.
The number of forces on the
skateboard is..
a. 0
b. 1
c. 2
d. 3
e.at least 4
Three objects are in contact as shown on a table
surface. Object 2, a woman, slid down the ramp until coming
into contact with object 3 and then stopped where she is. There
are no other objects on the table.
Identify the
number of forces
acting on object 3
a. 0
b. 1
c. 2
d. 3
e. 4
f. 5
A boy and a dog each have the same mass. The boy rides a
skateboard as shown. The dog rides a surfboard as
shown. Each moves with constant speed horizontally.
Which of the following is true?
a. Both the dog and the boy exert
force on their boards.
b. The boy exerts a force on the
skateboard, but the dog exerts no
force on the surfboard.
c. Neither of them exerts a force
on their boards because they are
moving horizontally.
Three objects are in contact as shown on a table
surface. Object 2 slid down the ramp until coming into
contact with object 3 and then stopped where it is. There
are no other objects on the table.
Identify the number of forces acting on object 3.
a. 0
b. 1
c. 2
d. 3
e. 4
f. 5