Science Assessment ~ Items ~ RG075003

A person places two magnets on a table and starts to bring them closer together until she feels them repel each other. Then she lets go of one of the magnets. When she lets go of the magnet, it moves away from the other magnet. Where did the kinetic energy (motion energy) of the magnet that is moving come from?

The magnetic force that was between the two magnets was transformed into the kinetic energy of the magnet that is moving.
Some of the potential energy that the system of magnets had when they were being held close together was converted to kinetic energy when she let go of the magnet.
Gravity gives magnets potential energy, and some of this energy was transferred to the magnet she let go of and converted to kinetic energy.
The magnet that she let go of created its own kinetic energy by moving.

Details
Performance
NGSS

Topic
Correct Answer: B
Misconceptions

Distribution of Responses

Chart showing distrubtion of responses for Item 075003

Scale Score for Item Difficulty (200[Easy]-800[Difficult]): 511

Students Responding Correctly

Group	Correct	Total	Percent
Overall	420	1130	37%
Grades
4–5	N/A	N/A	N/A
6–8	240	634	38%
9–12	180	496	36%
Gender
Male	202	518	39%
Female	211	592	36%
Primary Language
English	373	987	38%
Other	39	121	32%

View data table

Disciplinary Core Ideas: PS3.B When the motion energy of an object changes, there is inevitably some other change in energy at the same time.
PS3.C When two objects interacting through a field change relative position, the energy stored in the field is changed.

Science Assessment

Item RG075003: When two repelling magnets are let go, some of the potential energy that the system of magnets had when they were being held close together is converted to kinetic energy when let go.