2.  E k – the energy an object has because it is moving.

3.  The unit for kinetic energy is joule (J)

4.  E k – the energy an object has because it is moving.  The unit for kinetic energy is joule (J)  E k = ½ mv 2

5.  E k – the energy an object has because it is moving.  The unit for kinetic energy is joule (J)  E k = ½ mv 2m = mass in kg v = speed in ms-1

6.  The greater the mass of a moving object, the greater the kinetic energy of the object.

7.  If the mass of an object doubles, and the speed remains the same, the kinetic energy will double too.

8. 1. Calculate the kinetic energy of the truck shown below: Mass = Speed = 5ms -1 1000kg

9.  E k = ½ mv 2  ½ x 1000 x 5 2 = 12500 J

10.  The faster an object moves, the greater its kinetic energy.

11.  When the speed of an object doubles, and the mass remains the same, the kinetic energy is four times what it was.

12.  The faster an object moves, the greater its kinetic energy.  When the speed of an object doubles, and the mass remains the same, the kinetic energy is four times what it was.  This is because the amount of kinetic energy is related to the square of the speed.

13.  So, if the speed doubles, E k increases to 4 times its original value (2 2 = 4)

14.  If the speed increases 3 times, what’s the kinetic energy increase to?

15.  So, if the speed doubles, E k increases to 4 times its original value (2 2 = 4)  If the speed increases 3 times, what’s the kinetic energy increase to?  9 times original value (3 2 = 9)

16.  There is a car travelling at 3 different speeds below. The car and its driver has a mass of 1000kg. Calculate the kinetic energy for each of the speeds.   1ms -1  2ms -1  3ms -1

17.  This is important in car safety – if a car doubles its speed, there is 4 times the amount of kinetic energy to lose before the car is stationary.

18.  = a car travelling 100km/h has four times the distance to stop than if it was travelling at 50km/h

19. EkEk ½ m v 2

20.  From the triangle before, to calculate mass, use 1/2m = E k then m =2 x ½ m v 2

22. Two cars travelling down the road both have a 30000J of kinetic energy. 1. One car is travelling at 25ms-1 (90km/h). Calculate its mass. 2. The other car has a mass of 1000kg. Calculate its speed.

23. 1. 1/2m = E k v 2 300’000 = 480 252 then m =2 x ½ m m = 2 x 480 = 960kg

25.  At an athletics meet, the winner of the men’s 100m sprint crossed the line running at a speed of 10ms-1. If his mass was 80kg calculate his kinetic energy.