Forces, Motion, and Energy
Motion and Interaction
Why motion changes
Motion changes when forces act on an object. A net force causes acceleration, which means a change in velocity. Velocity includes both speed and direction.
Core mechanics terms
Newton's second law
The relationship means a larger net force produces a larger acceleration for the same mass.
If the net force on an object is zero, what happens?
Zero net force means no acceleration, so velocity stays constant.
Correct answer: It continues with constant velocity or remains at rest
What is the difference between speed and velocity?
Velocity is a vector quantity.
Correct answer: Speed is how fast something moves; velocity includes direction.
Forms of energy
Kinetic
- Energy of motion
- Depends on mass and speed
- Example: a rolling ball
Potential
- Stored due to position or condition
- Can be gravitational or elastic
- Example: water behind a dam
Which equation represents kinetic energy?
Kinetic energy depends on mass and the square of speed.
Correct answer:
Why does an object at a higher position often have more gravitational potential energy?
Higher position means more stored energy relative to a reference level.
Correct answer: Because gravity can do more work as it falls.
Energy is conserved
Energy can change form and move between objects, but in an isolated system the total amount of energy remains constant.