DASI-P - Rolling Drop Selected Response

What important physics idea is this question targeting?

This question assesses whether or not students understand how friction from air resistance will affect the motion of an object. (I)
This question assesses whether students can distinguish between vertical motion and horizontal motion in projectile motion — basically that forward motion and downward acceleration are independent of each other. (C)
This question gets students thinking about how objects fall when released from moving systems. (V)

Which answer best describes what student A's response indicates about their physics understanding?

This student understands that gravity is the only force after release, but has forgotten about that the hand was initially pushing the coin forward when it was being held and that this force is still pushing the coin forward, too. (I)
Their reasoning suggests they equate force direction with motion direction — assuming that because the net force is vertical, the motion must be vertical, revealing a misunderstanding of inertia and projectile motion. (C)
This response shows the student is comfortable attributing motion to force to explain the motion in terms of physical interactions. (V)

Which of the following options would best support Student A in being able to correctly respond to this question?

I would have students recreate the motion using our class rolling chairs and a beanbag, ideally using a camera to capture the trajectory in slow motion. She could see that the beanbag moves forward and there was a forward force acting on the coin in addition to gravity. (C)
I would have this student push a force sensor on a cart and examine what it reads as soon as someone stops pushing. (We probably did that already, so we would revisit this!) She should see that the cart keeps moving forward and the force reads zero. We would then predict whether that should be the same for the coin. (I)
I’d design an activity where students share and debate their different ideas about gravity. That way, they can hear each other’s thinking and come to a better understanding. (V)

Which answer best describes what student B's response indicates about their physics understanding?

The student understands that the coin will have an arc to its path, and they are showing how projectile motion influenced by both vertical and horizontal forces. (I)
The student is thinking intuitively about how it feels to move through the air and feeling the wind pushing you back. However, they haven't considered that this wind force will just slow down the forward motion, not immediately reverse its direction. (C)
The student is using everyday experience with wind and falling objects to create a motion model, which shows real-world connection. (V)

Which of the following options would best support Student B in being able to correctly respond to this question?

Assuming we've already talked about Newton's Laws, I'd ask students to use the force diagram this student drew to predict what would happen to something that is moving backwards, not moving, and moving forwards. We would then consider which one applies to the start of this scenario. (C)
I would show a video I often use of a ball being thrown up and then caught from the bed of a moving pick up truck. While the wind does affect it slightly, the ball lands in the bed of the truck. This would help them see why the force from the wind is not strong enough to cause the coin to be very affected. (I)
We would have a whole-class brainstorm on what forces are acting on the coin before and after it is dropped, and make a word wall of those forces.. (V)