Velocity-time graphs In this section you will be introduced to the difference between speed and velocity be introduced to velocity-time graphs and how to interpret them use the equation to calculate acceleration begin to relate acceleration and distance travelled to velocity-time graphs

Velocity and speed are similar but not the same. Look at the example below:- both balls may have the but they travel in different . The velocity of an object is its speed in a stated___________

Velocity and speed are similar but not the same. Look at the example below:- both balls may have the same speed but they travel in different directions. The velocity of an object is its speed in a stated direction

speeding up Here we are dealing with VELOCITY-time graphs. A steady velocity produces a ____________ line. A slope tells us that the car is speeding up or ______________. A steeper slope means a bigger ______________.

constant speeding velocity up time time time Here we are dealing with VELOCITY-time graphs. A steady velocity produces a horizontal line. A slope tells us that the car is speeding up or accelerating. A steeper slope means a bigger acceleration.

acceleration = change in velocity time 1 A car accelerates from 0 to 20m/s in 10seconds. Work out the acceleration of the car Acceleration = Acceleration =

acceleration = change in velocity time 2 A car accelerates from 5m/s to 20m/s in 5seconds. Work out the acceleration of this car Acceleration = Acceleration =

2 1 = (2m/s ) Answers 2 2 = (3m/s )

0-60 IN 6SECONDS (60mph = 25m/s) PINK CAR 0-60 IN 10 SECONDS BLUE CAR

A B Velocity m/s 25 Use the formula to work out the acceleration of the 2 cars 20 Acceleration of A is from 0 to 25m/s in 6 seconds 15 Acceleration of B is from 0 to 25m/s in 10 seconds 10 accel. of A = = 5 accel. of B = = Time in seconds 2 4 6 8 10

A B Velocity m/s 25 Use the formula to work out the acceleration of the 2 cars 25/6 = 4.166m/s 2 20 Acceleration of A is from 0 to 25m/s in 6 seconds 15 Acceleration of B is from 0 to 25m/s in 10 seconds 10 25/10 = 2.5m/s 2 Now calculate the gradient of these 2 lines. What do you notice? 5 The gradient of the line is the acceleration Time in seconds 2 4 6 8 10

The car travels at 12 m/s for 10 seconds. Use the formula to find out the distance it travels Higher level – you need to know that the area under a velocity – time graph is the distance travelled velocity 12 The area under a velocity-time graph is the distance travelled by the object 5 10 time Distance travelled = X = area underneath the graph = X =

The car travels at 12 m/s for 10 seconds. Use the formula to find out the distance it travels Higher level – you need to know that the area under a velocity – time graph is the distance travelled velocity Distance = 12 x 10 = 120m 12 Area = 12 x 10 = 120m 5 10 time The distance travelled = the area under the graph

Work out how far this car has travelled in 40 seconds! velocity Work out how far this car has travelled in 40 seconds! 25 B C A 10 20 30 40 time Area of A = X X = Area of B = X = Area of C = X X = Total area = + + =

Work out how far this car has travelled in 40 seconds! velocity Work out how far this car has travelled in 40 seconds! 25 B = 500m C = 125m A = 125m 10 20 30 40 time Start Answer = 125 + 500 + 125 = 750m

Summary Acceleration is the in velocity divided by the The acceleration can also be found by working out of the velocity-time graph The distance travelled can also be found by working out the under a velocity-time graph

Summary Acceleration is the change in velocity divided by the time. The acceleration can also be found by working out gradient of the velocity-time graph The distance travelled can also be found by working out the area under a velocity-time graph

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