ACT Preparation / Unit 22 ACT 2120 worked example, 60 to 90 seconds
Following Energy Through a System
The idea
An energy question is answered in three steps. First, list the forms of energy at the start: motion, height, heat, chemical, electrical. Second, list them at the end. Third, account for the change: the total stays constant, so any energy that seems lost has changed form, often to heat through friction.
In practice
Worked example: a ball is released from rest at the top of a ramp. At the top, its energy is gravitational potential energy; at the bottom, it has kinetic energy instead, minus a little lost to heat through friction. If the ball had 10 joules of potential energy at the top and 9 joules of kinetic energy at the bottom, then 1 joule became heat, and the total is still 10.
Where people slip
A passage reporting less useful energy at the end has not broken the conservation law. Look for where the difference went: heat, sound, or a change of shape.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
Unlocks
- Nothing yet depends on this.
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