P2 – Forces and Motion Lesson 3: D-T and V-T Graphs

Q1. A child goes out to visit a friend. The graph shows the child’s journey. (a) Calculate the child’s average speed for the whole journey. [Show your working and give the units in your answer.] (3) (b) How many times faster is the child travelling in part A of the graph than in part C? (2) (Total 5 marks) a. 140/70 = 2m/s b. 100/20 = 5m/s 40/20 = 2m/s 5/2 = 2.5 times A B C

Distance-Time Graphs: The gradient = speed Flat section are where it’s stopped The steeper the slope, the faster it is going Curves represent acceleration Keywords: Distance-Time, Velocity-Time, Gradient, To know the difference between speed and velocity. To be able to calculate speed. To be able to calculate acceleration.

Calculating Speed You can use a distance-time graph to calculate the speed. All you need to do is work out the gradient. Gradient = Vertical Horizontal Keywords: Distance-Time, Velocity-Time, Gradient, To know the difference between speed and velocity. To be able to calculate speed. To be able to calculate acceleration. Time (hours) Distance (miles) x e.g = 30 mph (Remember to use the units on the axis)

Q2. The graph shows the speed of a runner during an indoor 60 metres race. (a) Calculate the acceleration of the runner during the first four seconds. ( 3) (b) How far does the runner travel during the first four seconds? (Show your working.) (3) (c) At the finish, a thick wall of rubber foam slows the runner down at a rate of 25 m/s 2.

Velocity-time Graphs: The gradient = acceleration Flat section are travelling at a steady speed The steeper the slope, the greater the acceleration. Uphill sections are acceleration. Downhill section are deceleration The area under any section is the distance travelled in that time interval. A curve means a changing acceleration. Keywords: Distance-Time, Velocity-Time, Gradient, To know the difference between speed and velocity. To be able to calculate speed. To be able to calculate acceleration.

How to calculate speed: How to calculate velocity: How to calculate acceleration: Speed and Acceleration What I need to know. Definitions of key words: Speed: Velocity: Acceleration: Units MetresKilometres DistanceMetres (m) TimeHours (h) Speed and Velocity Metres per second (m/s) Acceleration

Distance-Time graphs: You can calculate the velocity using a d-t graph by: Speed-Time graphs: You can calculate acceleration by: You can calculate the distance travelled by: Velocity/TimeDistance/Time Stopped Constant Velocity Constant Acceleration D t D t D t V t V t V t

How to calculate speed: Speed = distance time How to calculate velocity: Velocity = distance time How to calculate acceleration: Acceleration = Change in Velocity time Δv = change in velocity (e.g. if a car accelerates from 30m/s to 70m/s, its change in velocity is 40m/s. Speed and Acceleration What I need to know. Definitions of key words: Speed: The time is takes to travel a set distance. Velocity: Acceleration: Units MetresKilometres DistanceMetres (m) TimeHours (h) Speed and Velocity Metres per second (m/s) Acceleration d s t Δv a t d v t Same as speed but tells you what direction the motion is in. The time it takes for change speed. Seconds (s) m/s 2 Kilometres (km) Kilometres per hour (km/h) km/h 2

Distance-Time graphs: You can calculate the velocity using a d-t graph by: Working out the gradient of the graph, i.e. distance/time. Gradient = Vertical Horizontal Speed-Time graphs: You can calculate acceleration by: Working out the gradient of the graph, i.e. speed/time. You can calculate the distance travelled by: Working out the area under the graph. Velocity/TimeDistance/Time Stopped Constant Velocity Constant Acceleration D t D t D t V t V t V t

Are you now able to…. I still feel unsure. I need some more help to understand. I feel ok. I need to do some more work to check my understanding. I am happy and feel I understand and can explain the main points. To be able to draw and use a Distance- Time graph To be able to draw and use a Velocity- Time graph To be able to calculate acceleration and speed using graphs. Keywords: Distance-Time, Velocity-Time, Gradient,