Motion Graphs

1. Speed.. m or cm/second m or cm secondsS D T Examples using the Speed Formula (Showing full working): 1. The sprinter ran 100 metres in 10 seconds. What was his speed ? 2. The porsche travelled at 40 m/s for 2 minutes. How far did it go ? Nb VELOCITY (v)is simply speed in a given direction DISPLACEMENT (S) is the distance in a given direction

2. Acceleration The acceleration of something tells us how quickly its speed is changing. We can say that acceleration is the amount ………..changes per …….…...speedsecond metres/second 2 metres/second seconds A SS T 1. The ferrari was travelling at 20 m/s behind a lorry. It pulled out to overtake and accelerated at 4 m/s 2 for 2 seconds. What was its new speed ? New Speed = Old Speed + Change in Speed = 20 m/s + 8 m/s= 28 m/s or Where v = final velocity u = initial velocity

4. Motion Represented on Graphs. There are two types of motion graphs, and three types of motion. Best represented in a table. Velocity/TimeDistance/Time Stopped Const’ Velocity Const’ Accel’n D t D t D t V t V t V t Gradient = VelocityGradient = Accel’n Area = Distance travelled Question Velocity Time Graph for parachutist V (m/s) T (s) A. What was his acceleration from 0 to 15 sec ? B. What was happening at 50 seconds? He had just opened his parachute and was decelerating. C. Approximately how far did he fall altogether? Area under graph  50   15 = 8250m

Distance time graphs ;Summary n The gradient of a distance time graph gives the velocity n increasing gradient means object is accelerating n decreasing gradient means object is decelerating n zero gradient means object is stationary

Velocity time graphs; Summary n The gradient of a velocity time graph gives the acceleration of an object n the area under a velocity time graph gives the total distance traveled n Increasing or decreasing gradient gives the rate at which the acceleration is increasing or decreasing n Zero gradient means the object is travelling at constant speed

Problems 1. Calculate the speed over OA AB and BC 2. Calculate (a)the acceleration over OA, AB and BC (b) the total distance traveled in the 12 s 5, 0, 3.75m 5m/s 2, 0, 3.75m/s 2, 127.5m