Open-ended questions in web-survey/Interview
0401 #1
Q1: As shown in the figure below, a collision happens between a big truck and a car. The
big truck has a much larger weight than the car does. Before the collision, both vehicles
are traveling at a same constant speed. Discuss the forces exerted by the truck on the car
and by the car on the truck at the moment they collide.
Then one of your group member says “Both the truck and the car exerts a force on the other vehicle but the
truck exerts a larger force because the truck has more mass is going to do more damage to the car and the
car will be pushed back.”
How do you think about the students’ reasoning?
“Force is calculated my multiplying mass by acceleration. If both the truck and the car are traveling at the
same acceleration than the only way for the force to not be equal is find which has the larger mass.”
“Since a=F/m, and they are traveling at the same speed, the mass is the only independent variable. Since the
truck has much more mass, it exerts a much larger force on the car than the car on the truck.”
“Because force=mass*acceleration, and acceleration for both vehicles is equal, the car with more mass will
do more damage.”
“The truck is more massive and F=MA says that the truck will exert more force on the car than vice-versa.”
“The truck has a larger mass than the car, so the truck is going to exert a larger force on the car than the car
will on the truck when they collide. Then by using Newton's law "Objects in motion tend to stay in
motion", the truck with the larger mass will want to stay in motion more than the car, so the truck will push
the car backwards”.
“I agree with the student’s reasoning based on Newton’s second law. The truck’s force will be greater than
the car’s simply because it has more mass than the car and they are traveling the same velocity.”
“I recite the equation F = ma. First, if an object has a mass and acceleration, a force will be produced. Since
the cars will be colliding, they with both slow considerably, so they will have acceleration. Second, since
the truck has a much larger mass, it will produce a much larger force.”
0401 #2
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Q2: Two boys, Jimmy and Max, are tossing identical marbles at each other. The Max is a
little stronger than the Jimmy, so the marble from him goes faster than the marble from
Jimmy. During one nice shot, the two marbles, one from the Max and one from the
Jimmy, collide in mid air (see figure below). Discuss the forces extorted by and on the
two marbles when they collide.
Then one of your group member says “Both marble exerts a force on the other marble
Max’s marble exerts a larger force because Max is stronger and has a larger initial throw,
and his marble moves faster and will push on Jimmy’s marble harder. If Max’s marble
has a much faster speed, it can even push Jimmy’s marble to move backward (to the right
direction).”
How do you think about the student’s reasoning?
“Max's marble had a greater force on it from the beginning thus giving it a higher velocity and momentum
than Jimmy's marble. So when they hit, Max's marble does exert a greater force on Jimmy's.”
“The marble with the larger velocity will exert the larger force, and that is Max's marble. Then once again
using Newton’s law "Objects in motion tend to stay in motion", Max's marble, with the higher velocity,
will want to stay in motion more, so it could push Jimmy's marble backwards.”
“The student is correct. If two identical marbles are thrown at each other, one with a greater initial velocity,
the faster marble will exert a greater force on the other.”
”[in this case, faster means larger acceleration]
“I think that his reasoning concerning the evidence is logical. When you look at the force=mass x
acceleration you notice that the masses of the two objects are the same and the acceleration of Max's
marble is going to be more then Jimmy's Marble.”
“Since they are of the same mass, but one has a larger speed, it will have a larger acceleration when the two
collide, and the larger force produced by the faster marble will have probably force jimmy's marble to
move backward.”
“If Max is stronger then his marble will have a greater acceleration. This means that Max's marble will
have a greater force pushing on Jimmy's marble than Jimmy's marble will have pushing on Max's marble.”
“Since max threw it harder, it would have a larger force, and therefore since and the masses are the same,
then the acceleration of Max's marble is greater and will push jimmy's back.”
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“Since the problem stated that they have equal mass but Max is stronger and his is moving faster, it can be
determined that his will have a greater force on the other marble then Jimmy's marble will have on Max's.”
“Max's marble travels faster because he is stronger, it has a bigger acceleration. So it would exert more
force.”
“F = ma. I agree with the above statement. The force exerted by Max’s marble is greater than the force
exerted by Jimmy’s marble because it is moving faster.”
“I agree because since they are of the same mass, but one has a larger speed, it will have a larger
acceleration when the two collide, and the larger force produced by the faster marble will have probably
force jimmy’s marble to move backward.”
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0401 #3
Q3: Two students, Amy and Jane, are on very good identical roller blades facing each
other. They both have a same mass of 50 kg. Amy places her hand on Jane, as shown to
the right. Amy then suddenly pushes outward with her hand, causing both to move. In
this situation, while Amy’s hands are pushing Jane, discuss the forces between them?
Then student A from your group says “Only Amy exerts a force on Jane since she is the
person who is pushing.” Student B disagrees and says “Both exerts a force on the other
but Amy may exerts a larger force depending on how she pushes, you know, she can sort
of bent down a little and pushes very hard on Jane and make Jane move back a lot.”
How do you think about the two students’ reasoning?
“Both Amy and Jane exert a force on each other but depending on how Amy pushes, her force could
possibly be greater. Both have the same mass but the acceleration is not mention to determine the force,
that is why Jane may move faster.”
“There would be forces exerted on both people. But depending on how the person was pushed, Amy could
be exerting a larger force than Jane.”
“I am with student B. They both exert a force on each other because of the fact that they are touching and a
force was being exerted by one of them. That force will actually affect the position of both.”
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