Motion Speed and Velocity Acceleration Graphical Representation of

Motion Speed and Velocity Acceleration Graphical Representation of Motion Uniformly Accelerated Motion Falling Bodies Momentum AS Physics

Describing Motion Time Interval – Time taken to travel a certain distance Distance – How far the object has traveled Displacement – Distance + direction – Final position – initial position 22

Describing Motion t=0 s x 1 =5 m 30 m t=3 s x 2 =35 m 3

Position-Time Graph 4

Speed and Velocity Average Speed – Total distance traveled divided by time taken Instantaneous Speed – Small distance traveled divided by small time taken Average Velocity – displacement divided by total time Instantaneous Velocity – Rate of change of displacement at an instant 5

Velocity on a Graph • Gradient of the secant line on an s-t graph èChange in position over time interval èAverage velocity 6

Velocity on a Graph 7

Velocity on a Graph • Gradient of a tangent on an s-t graph èChange in position over time interval (Δt 0) èInstantaneous velocity • Area under the graph èdisplacement 8

Example Find the average velocity of the car Calculate the instantaneous velocity at 0 s, 5 s and 25 s 99

Interpreting Graphs 1 10

Interpreting Graphs 2 11

Acceleration Rate of change of velocity – (Final velocity – initial velocity) divided by time Change in magnitude of velocity – Speeding up – Slowing down Change in direction of velocity Change in both magnitude and direction 12 12

Acceleration on Graphs • Gradient of a secant line on a v-t graph l Average acceleration • Gradient of a tangent line l Instantaneous acceleration 13 13

Interpreting Graphs 3 14

Uniformly Accelerated Motion Equations u = initial velocity v = final velocity a = constant acceleration t = time taken from start s = displacement 15 15

Uniformly Accelerated Motion • Examples èPage 42 • Car Stopping Distances èThinking distance § Car travels at constant speed èBraking Distance § Car decelerates èStopping Distance § Thinking Distance + Braking Distance èMake comparisons for initial speeds 20 and 40 metres per second (page 40) 16 16

Falling Bodies • Free Fall Constant downwards acceleration l Gravitational acceleration l 9. 81 ms-2 l Equations l • Air Resistance Proportional to surface area l Proportional to speed l Terminal velocity l Graph (page 45) l 17

Projectile Motion • Horizontal Motion Constant velocity l Equation l • Vertical Motion Free Fall l Constant acceleration l Acceleration due to gravity l Equations l • Examples 18