Motion

1. Speed=distance*time

2. Mass is constant, weight change

3. moment=force*perpendicular distance between axis of rotation and line and action of force.

4. pressure=force/area of contact surface unite n/m方 or Pa(Pascal)

5. Types of motion

5.1. Oscillatory motion （摆动）

5.2. Rotational motion （转动）

5.3. Trans;lational motion （平移）

6. Scalar and vector

6.1. Scalar is quantities that only have magnitude but no direction

6.2. Vector is quantities that have a magnitude and direction

6.3. Displacement is 位移

7. force=k*extension of spring