1. A physical quantity is one that can be measured, or calculated, and expressed in numbers.
2. A scalar quantity is one with magnitude only. It has no directional component.
3. The distance between two points is a measure of how far one point is from the other.
4. Time is used to measure the duration of events, to put them in sequence or to measure the interval between them.
5. Speed is the distance travelled per unit time. 6. A vector quantity is one with both magnitude and direction. 7. Displacement is distance in a given direction. 8. Velocity is the rate of change of displacement with respect to time. 9. Acceleration is the rate of change of velocity with respect to time.
10. Mass is a measure of the amount of matter in a body. 11. Momentum is the product of mass and velocity. 12. A force is that which can cause acceleration.
13. Acceleration due to gravity is the acceleration experienced by a body in free fall within the gravitational field of a massive body.
14. Weight is a force equal to the product of mass and acceleration due to the gravity. 15. Centre of gravity is the point at which the whole weight of a body appears to act. 16. Friction is a force that opposes the motion of a body.
17. The moment of a force is the force multiplied by the perpendicular distance to the fulcrum.
18. A lever is a rigid body that is free to rotate about a fixed axis.
19. A couple is a pair of equal and opposite forces whose lines of action do not coincide.
20. The torque of a couple is equal to the magnitude of one of the forces multiplied by the distance between them.
21. Density is mass per unit volume. 22. Pressure is force per unit area.
23. Buoyancy is the upward force on a body that is wholly or partially immersed in a fluid.
24. Work is the product of force and displacement. 25. Energy is the ability to do work.
