OCR 21st Century Science Unit P4a Revision Motion

Distance, Speed and Time Speed = distance (in metres) time (in seconds) Freddie walks 200 metres in 40 seconds. What is his speed? Hayley covers 2km in 1,000 seconds. What is her speed? How long would it take Lauren to run 100 metres if she runs at 10m/s? Jake travels at 50m/s for 20s. How far does he go? Izzy drives her car at 85mph (about 40m/s). How long does it take her to drive 20km? 5m/s 2m/s 10s 1000m 500s

Distance-time graph

Distance-time graph 2) Horizontal line = 40 30 20 10 4) Diagonal line downwards = Distance (metres) 3) Steeper diagonal line = Time/s Diagonal line = 20 40 60 80 100

Distance-time graph summary

40 30 20 10 20 40 60 80 100 Distance (metres) Time/s 30/12/2018 Distance (metres) Time/s 20 40 60 80 100 What is the speed during the first 20 seconds? How far is the object from the start after 60 seconds? What is the speed during the last 40 seconds? When was the object travelling the fastest? 0.5m/s 40m 1m/s 40-60s

40 30 20 10 20 40 60 80 100 Distance (metres) Time/s 30/12/2018 Distance (metres) Time/s 20 40 60 80 100 What was the velocity in the first 20 seconds? What was the velocity between 20 and 40 seconds? When was this person travelling the fastest? What was the average speed for the first 40 seconds? 1.5m/s 0.5m/s 80-100s 1m/s

Distance-time graph for changing speeds 40 30 20 10 Object is speeding up here Object is slowing down here Distance (metres) Time/s 20 40 60 80 100

Acceleration V-U T A Acceleration = change in velocity (in m/s) 30/12/2018 V-U T A Acceleration = change in velocity (in m/s) (in m/s2) time taken (in s) A cyclist accelerates from 0 to 10m/s in 5 seconds. What is her acceleration? A ball is dropped and accelerates downwards at a rate of 10m/s2 for 12 seconds. How much will the ball’s velocity increase by? A car accelerates from 10 to 20m/s with an acceleration of 2m/s2. How long did this take? A rocket accelerates from 1,000m/s to 5,000m/s in 2 seconds. What is its acceleration? 2m/s2 120m/s 5s 2000m/s2

Acceleration V-U T A Acceleration = change in velocity (in m/s) 30/12/2018 V-U T A Acceleration = change in velocity (in m/s) (in m/s2) time taken (in s) Will accelerates from standstill to 50m/s in 25 seconds. What is his acceleration? Pierre accelerates at 5m/s2 for 5 seconds. He started at 10m/s. What is his new speed? Elliott is in trouble with the police. He is driving up the A29 and sees a police car and brakes from 50m/s to a standstill. His deceleration was 10m/s2. How long did he brake for? Another boy racer brakes at the same deceleration but only for 3 seconds. What speed did he slow down to? 2m/s2 35m/s 5s 20m/s

Acceleration summary

Velocity-time graphs

Velocity-time graphs 1) Upwards line = 80 60 40 20 4) Downward line = 30/12/2018 1) Upwards line = 80 60 40 20 4) Downward line = Velocity m/s 3) Upwards line = 2) Horizontal line = T/s 10 20 30 40 50 30/12/2018

How fast was the object going after 10 seconds? 80 60 40 20 30/12/2018 Velocity m/s T/s 10 20 30 40 50 How fast was the object going after 10 seconds? What is the acceleration from 20 to 30 seconds? What was the deceleration from 30 to 50s? 40m/s 2m/s2 3m/s2

How fast was the object going after 10 seconds? 80 60 40 20 30/12/2018 Velocity m/s T/s 10 20 30 40 50 How fast was the object going after 10 seconds? What is the acceleration from 20 to 30 seconds? What was the deceleration from 40 to 50s? 10m/s 4m/s2 6m/s2

Velocity-time graphs summary