Download 8th Grade Student Test - Force and Motion

Force and Motion Student Test
8th Grade
Part I: Multiple Choice
Choose one correct answer for each of the following questions.
1. You are watching the flight of a small, remote-control model airplane as it flies in a haphazard path
over an empty football field. Which of the following statements about the motion of the plane is
correct?
a. When the plane flies through the point from which it started, the distance the plane has
traveled is zero.
b. When the plane flies through the point from which it started, the change in position for the
plane is twice the distance traveled.
c. The distance traveled by the plane can be a positive or a negative number.
d. The distance traveled by the plane can only be a positive number.
2. Starting at a flagpole, you begin walking due East with equal strides for 200 strides. Then you
reverse direction and walk 100 strides directly back toward the flagpole. Now what is your
position?
a. 100 strides
b. 100 strides East of the flagpole
c. 300 strides
d. 300 strides East of the flagpole
3. An object moving with constant velocity must move in a…
a. straight path and experience larger and larger changes in position during each successive
second.
b. curved path and experience larger and larger changes in position during each successive
second.
c. straight path and experience equal changes in position during each successive second.
d. curved path and experience equal changes in position during each successive second.
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Figure 1: Velocity versus Time Graphs for Two Trains Moving in Straight Lines
A
v
B
0
t
4. Which of the following is true about the motion of the trains? (Assume that both trains are moving
in straight lines.)
a. Both trains are moving with a constant velocity.
b. Train “A” is moving with a constant velocity while the velocity of train “B” is increasing with
time.
c. Both trains have velocities that are increasing with time.
d. Train “B” is moving with a constant velocity while the velocity of train “A” is increasing with
time.
5. Choose the correct statement about the position versus time graphs that would correspond to the
velocity versus time graphs in Figure 1 above.
a. The position versus time graph associated with graph “A” must be curving while the position
versus time graph associated with graph “B” must be a straight line.
b. The position versus time graph associated with graph “B” must be curving while the position
versus time graph associated with graph ”A” must be a straight line.
c. The position versus time graphs associated with both graphs are curving.
d. The position versus time graphs associated with both graphs are straight lines.
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6. Which of the following is NOT an object experiencing acceleration?
a. An object which moves in a straight path and experiences equal changes in position during
each successive second.
b. An object moving at constant speed around a corner.
c. An object which moves in a straight path and experiences larger and larger changes in position
during each successive second.
d. An object which moves in a straight path and experiences smaller and smaller changes in
position during each successive second.
7. A race car is traveling around an oval track at a constant speed. At which point on the oval track
does the race car accelerate? See Figure 2 below.
Figure 2: Race Track
a. The car accelerates at point A
b. The car accelerates at point B
A
c. The car accelerates at point C
C
B
d. The car never accelerates.
Continue to the next page for #8.
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Figure 3: Timed Positions
Two balls, A and B, are moving as illustrated in the figure below. The numbers represent readings of
a clock in seconds. At each clock reading the position occupied by each ball is represented by a
large black dot. At clock time 1 ball A occupies the position marked 1, and ball B occupies the
position marked 1, etc. The arrows indicate the direction of motion of both balls. Each line is 1 meter
in total length.
A
1
2
3
4
5
6
B
A
1
2
3
4
5
Use Figure 3 to Answer #8-10
8. Which object(s) is(are) accelerating?
a.
b.
c.
d.
only A
only B
both A and B
Neither A nor B
9. Which object(s) could have only balanced forces acting on it (them)?
a.
b.
c.
d.
only A
only B
both A and B
neither A nor B
10. The motion of which object(s) would be represented by a curved line on a position
versus time (x versus t) plot?
a.
b.
c.
d.
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only A
only B
both A and B
neither A nor B
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Figure 4: Susan’s Walk to School
Susan picked up the pace as she left her front door and headed to school. She soon reached her usual
steady pace. About halfway to school she slowed to a stop and watched a bird building a nest. When she
realized she was late, she ran the rest of the way to school to avoid being marked late. She didn’t slow down
until she was stopped by the safety guard in front of the school.
A.
B.
V
v
t
t
C.
D.
v
v
t
t
11. Which VELOCITY VERSUS TIME graph In Figure 4 above shows Susan’s velocity during her walk
to school?
a. Graph “A”
b. Graph “B”
c. Graph “C”
d. Graph “D”
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12. For the situation described in Figure 4, we can conclude that Susan
a. did not accelerate while walking to school.
b. accelerated only once while walking to school.
c. accelerated twice while walking to school.
d. accelerated more than twice while walking to school.
13. What happens to the motion of an object if the original net force is tripled?
a. the velocity of the object is 3 times what is produced by the original net force
b. the acceleration of the object is 3 times what is produced by the original net force
c. the velocity of the object is 1/3 of what is produced by the original net force
d. the acceleration of the object is 1/3 of what is produced by the original net force
14. If acceleration decreases while the force stays the same then the mass must have:
a. increased.
b. decreased.
c. stayed the same.
Use Figure 5 on the next page to answer #15.
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Figure 5: Rocket Car
Imagine a car that is equipped with a rocket engine on a straight race track. The rocket engine
applies a large constant force that moves the car forward. Assume that the car motion is begun at
time (t) = 0 with a position (x) = 0. The motion of the car can be described by a position versus time
graph and a velocity versus time graph.
a.
x
v
t
b.
t
v
x
t
c.
x
t
v
t
t
v
d.
x
t
7
t
15. Which pair of graphs correctly describes the motion of the rocket car described in Figure 5?
a.
b.
c.
d.
Pair “a”
Pair “b”
Pair “c”
Pair “d”
16. The moon is attracted to the Earth so we know that…the Earth is …
a. the Earth is repelled by the moon.
b. the Earth is attracted to the moon.
c. the moon has no effect on Earth.
17. A friend is on a sled that is on very slippery ice (no friction). You apply a force and the sled
speeds up. Later that day two of your friends get on the sled. You push again making the sled
speed up. Which of the following statements is FALSE?
More force is required to speed up the sled with two friends because:
a.
b.
c.
d.
there is more mass.
there is more inertia.
there is no friction.
there is more gravity.
18. In the situation pictured below, student “A” weighs 150 pounds and student “B” weighs 100 pounds.
Student “A” gives student “B” a push. Which of the following is true about the situation?
a.
b.
c.
d.
Neither student exerts a force on the other.
Each student exerts a force on the other but “B” exerts the larger force.
Each student exerts a force on each other but “A” exerts the larger force.
Each student exerts the same amount of force on each other.
A
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B
Part II: Open Response
19. Horse jockeys must watch their weight because there are restrictions as to how
much weight a horse can carry in a race. For example, in the Kentucky Derby
horses are restricted to carrying 126 pounds. That total includes the weight
of the jockey and all the gear on the horse. If the jockey is too light the
officials will add weights to the gear so that all horses in the race are
carrying the same weight.
a. Describe Newton's Second Law of Motion.
b. Use Newton's Second Law of Motion to explain how increasing the weight a
horse carries would impact its ability to win the Kentucky Derby.
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