Forces and Motion

1. The only "natural" motion is for an object to be at rest.
2. If an object is at rest, no forces are acting on the object.
3. A rigid solid cannot be compressed or stretched.
4. Only animate objects can exert a force. Thus, if an object is at rest on a table, no forces are acting upon it.
5. Force is a property of an object. An object has force and when it runs out of force it stops moving.
6. The motion of an object is always in the direction of the net force applied to the object.
7. Large objects exert a greater force than small objects.
8. A force is needed to keep an object moving with a constant speed.
9. Friction always hinders motion. Thus, you always want to eliminate friction.
10. Frictional forces are due to irregularities in surfaces moving past each other.
11. Rocket propulsion is due to exhaust gases pushing on something behind the rocket.
12. Time is defined in terms of its measurement.
13. The location of an object can be described by stating its distance from a given point (ignoring direction).
14. The terms distance and displacement are synonymous and may be used interchangeably. Thus the distance an object travels and its displacement are always the same.
15. Velocity is another word for speed. An object's speed and velocity are always the same.
16. Acceleration is confused with speed.
17. Acceleration always means that an object is speeding up.
18. Acceleration is always in a straight line.
19. Acceleration always occurs in the same direction as an object is moving.
20. If an object has a speed of zero (even instantaneously), it has no acceleration.