Key Idea: When objects collide, contact forces can transfer energy from one object to another resulting in a change in the objects’ motion.
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Energy can be transferred electrically when an electrical source is connected in a complete circuit to an electrical device.
These items have been aligned to more than one key idea. To view the sub-ideas click on a key idea below.
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When objects collide, contact forces can transfer energy from one object to another resulting in a change in the objects’ motion.
Students should know that:
- When two objects collide, their speeds change compared to their speeds before the collision and energy is transferred from the object that slows down to the object that speeds up. [Note: An exception to this is when two identical objects collide at a 45-degree angle. Assessment items will not assess students’ understanding of the exceptions.]
- Energy is transferred by forces as long as one object exerts a force on another object. The transfer of energy stops when one object no longer exerts a force on the other object.
- When two forces act over the same distance and in the same direction, the stronger force transfers more energy than the weaker force.
Boundaries:
- This idea is limited to transfers of energy as a result of direct contact forces and elastic collisions and is limited to systems containing two objects that are moving or that can be moved. Examples of direct contact include when billiard balls hit each other, when a ball is thrown or kicked, when a baseball or golf ball is hit with a bat or club, when an object is set in motion by a rubber band or spring, or when a bobsled or swing is pushed.
- Assessment items include contexts where there is a clear transfer of energy (one object will slow down and the other will speed up). Items do not include collisions between objects that are significantly different in mass where the change in speed of the more massive object is negligible.
- For direct contact interactions, assessment items may include situations where both objects are moving or one object is moving and the other object is at rest.
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Energy can be transferred electrically when an electrical source is connected in a complete circuit to an electrical device.
Students should know that:
- Electrical sources, such as batteries or generators, can transfer energy to electrical devices, such as a light bulbs, speakers, heaters, or motors, when they are connected in a complete conducting circuit [a complete path of conductors through which an electric current can travel].
- If the electrical circuit is not complete, energy will not be transferred from the electrical source to the electrical device.
- The transfer of energy electrically can produce motion, sound, heat, or light.
Boundaries:
- This idea is not quantitative. Assessment items do not ask students to calculate how much energy is transferred electrically in a particular situation (e.g. Power = current X voltage).
| Item ID Number |
Knowledge Being Assessed | Grades 4–5 |
Grades 6–8 |
Grades 9–12 |
Select This Item for My Item Bank |
|---|---|---|---|---|---|
56% | 52% |
58% |
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Misconception |
Student Misconception |
Grades 4–5 |
Grades |
Grades |
|---|---|---|---|---|
Energy cannot be transferred electrically from one place to another (AAAS Project 2061, n.d.). | 15% | 20% |
19% |
Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.
Code |
Statement |
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When objects collide, the contact forces transfer energy so as to change the objects' motions. |