Physics Chapter 2 Notes

1. Physics Chapter 2 Notes Speed, Velocity, and Acceleration

2. Displacement • The distance in a straight line in a certain direction from the starting point • Eg Lily walked 1km to the North, then 2km to the East followed by 1km to the south. • a. what is her total walking distance? • b. what is her final displacement? • Answers: • a. 1 + 2 + 1 = 4km • b. 2m due east from starting point

3. Speed and Velocity • Scalar: has only magnitude and no direction • Speed isdistance travelled by a body per unit time • Vector: has both magnitude and direction • Velocity is distance travelled per unit time in a stated direction • Units: ms-1 or kmh-1 • Average speed is NOT the constant speed • Instantaneous speed: the speed at any instant • Use speedometer to find instantaneous speed • Can be found by finding the gradient of the tangent to the displacement-time graph, at that point in time

4. Speed measurement using ticker-tape timer

5. Acceleration • Defined as the rate of change of velocity with time • Units: ms-2 or kmh-2 • If velocity is constant, acceleration= 0 • If velocity decreasing  negative acceleration/deceleration • The gradient of a velocity-time graph of a moving object gives the acceleration of the object at a given time

6. Acceleration of bodies falling near to earth • An object falling near to Earth, where the air resistance is negligible, has a velocity-time graph that is s straight line. It falls with a constant acceleration • The only force acting on the object experiencing free fall is the force of gravity • Acceleration = 10ms-2

7. Acceleration-time graphs Decreasing acceleration Decreasing speed Constant speed

8. Velocity-time graphs Constant speed Constant speed Zero acceleration Constant acceleration Increasing acceleration

9. Distance-time graph

10. Area under velocity-time graph • Area under velocity-time graph is the distance