Questions…

Here are some challenging multiple choice questions I have asked my student this year… figured I’d share.

For each situation below, circle all of the statements that you would identify as accurate scientific statements about the situation. You can circle more than one explanation as scientifically accurate. If you think none of the statements are scientifically accurate, then select only that option.

Situation #1

A heavy stone and a light stone are dropped from the same height. Both reach the ground at the same time, because

(A) The gravitational force from the earth is the same on all objects independent of their mass

(B) All objects fall toward the earth with the same constant speed

(C) The heavy stone is so large that the air below it pushes up on it, causing it fall slower than it would otherwise

(D) Each stone experiences a downward force proportional to its mass

(E) I believe that none of the above explanations are scientifically accurate

Situation #2

A heavy cart moves quickly along a horizontal track and then crashes into a light cart, which is at rest. During the collision, the light cart changes its speed much more than the heavy cart changes its speed, because

(A) The heavy cart exerts a much larger force on the light cart than the light car can exert back on the heavy cart.

(B) The heavy cart carries with it a very large force that is imparted onto the light cart

(C) The light cart has such a small mass that it responds with a very large acceleration in response to the force exerted by the heavy cart.

(D) It is easier to change the motion of objects that are stationary than objects that already are moving.

(E) I believe that none of the above explanations are scientifically accurate

Situation #3

Two identical sleds move along frictionless tracks. One of the sleds is moving faster than the other sled. Circle any statements you believe to be scientifically accurate statements about the situation.

 (A) The faster sled carries with it a greater force than the slower sled does.

 (B) The faster sled must have experienced a larger force in the past that that slower sled experienced in the past.

 (C) The faster sled is currently experiencing a larger force that the slower sled is currently experiencing.

 (D) The faster sled must be lighter than the heavier sled.

 (E)  I believe that none of the above explanations are scientifically accurate.

 Situation #4:

A sled is pushed along a horizontal frictionless track in such a way that it speeds up at a constant rate. This could happen if

 (A) A constant force is applied to the sled in the direction of motion

 (B) A force of decreasing magnitude is applied to the sled in the direction of motion

 (C) A force of increasing magnitude is applied to the sled in the direction of motion

 (D) No forces are applied to the sled

 (E)  None of the above conditions would make it possible to speed up the sled.

What is force like?

The student quotes below are in response to the following prompt:

Explain why someone might think that objects can “have” force, or that you can “give” force to an object. Then explain why force is not like something you can have or give. In your own words, what is force like?

I’m curious about which is your favorite and why.

“Because people may be confused with the definition of momentum. They feel that if I give this object this much velocity because it has this much has then I can make it have a huge force when it impacts against something. You can’t give or have force because force is always there, there are different forces acting on everything. Force to me is this like a bully hat is always around and very active but you don’t notice until a bigger force is around to put that force in its place. Sort of… ok I’m not really good at explaining this.”

“Someone might think that objects have force because the objects are the source or cause of the reaction to the force. But, force is just a result from the movement or actions of an object and isn’t anything that an object can ‘have’ or ‘give’.”

“Someone can think that an object has force because when two objects collide they react to each other and this is motion is what people see as force. you cant have force or an item cant have force because force is the energy that is expelled when the items collide with each other. the energy that is expelled on the the second object is force and is only present when the items collide with each other.”

“Someone might think an object would have force because it contains  mass and could therefore put force onto another object. Force is not something you can have or give because it is just the attraction between two objects; it does not contain mass. I would describe force as a push or pull on an object that could cause it to move or accelerate due to some type of attraction between the objects.”

“Someone might think think that you can give force to an object because an object moves when someone pushes on it. You can’t give an item your force. When you put a force on an object it will move.”

“Someone might think that objects have force due to their mass when it pushes an object. Force depends on acceleration and mass, so without acceleration there would be no force even if it had a mass. With a constant velocity, the acceleration will equal 0 and there will be no force.

“One cannot have force because when one object exerts a force onto a second object the second object exerts a force of equal strength and opposite direction onto the first object. Force is like the ability to move objects.

“Someone might think that objects can have force, or that you can give force to an object because you can obviously push or pull something if you wanted to as well a heavy object pushing against you. However, force is not like something you can have or give because force is the direct interaction between two objects when a push or pull is done. You can not have force until it is acted upon an object. Therefore, force is an interaction between objects. The force of an object to another object is equal in opposite directions.”

“You could think that you can give something force because, when you apply force you may transfer it to the object. On the other hand force may just be being applied to the object. Force is what happens when two objects interact.”

“Force is not something you can just have or give away between two objects. It may be common to think it is due to the fact that is what many people have heard throughout their elementary science classes. However force is a relationship between two objects causing motion to occur. The way I think about force is if there is a heavy box on the ground and I am trying to push it I cant simply walk up to the box and touch it and expect it to move. I have to push with my legs against the ground and apply a force through my arms to push the box and cause a movement.”

Objects don’t have a force, a force is exerted on an object. People might think that you can give force to an object because when they push it or pull it them they think that is what would be considered force.”

“An example of someone thinking an object might have force would be pool. When you hit the que ball, you are giving it a force.

“Someone might think that an object “has” force if it doesn’t break when touched. For example, someone might say a chair is applying force when someone sits on it, since it doesn’t break. Someone might also think that by touching or pushing an object this adds force to it. Force is more of a measure to describe how the movement of an object changes – as the result of a change in the object’s mass or acceleration. It doesn’t describe what someone is doing to the object, but what happens as a result of someone’s contact with the object.”

“I think that people get force and momentum mixed up. momentum is determined by the mass and velocity of an object. A car at a low speed crashing into a wall is not going to cause as much force as for instance a 18 wheeler going at a higher speed. I think that’s what people think is force or that fact that you can give something force when really it is momentum. Also, I could apply force by pushing down on a button, but i am applying it not giving the button itself force. Force is an application or influence. It is not transferred, given, or something something already has.

“To me force is something that doesn’t happen until you exert it. If you push something you give it enough momentum to get to where its going, but if it hits something it will exert a force on that object and make that object go while the first object either slows down considerably or stops all together.”

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