1. Power is: The rate of doing work.
(and also) The rate of energy transfer. J/s or Watt (W)
Power =  W
 t

2. Power is: The rate of doing work.
(and also) The rate of energy transfer. J/s or Watt (W)
Power =  W
 t
Power =  W = F x displacement =
 t time

3. Power is: The rate of doing work.
(and also) The rate of energy transfer. J/s or Watt (W)
Power =  W
 t
Power =  W = F x displacement = F x velocity
 t time

4. Problem: A 20 tonne truck can move up a 12% gradient
at 50 mph. Calculate the truck’s power.
1. Calculate mass (1000kg = 1 tonne)
2. Calculate weight ( 10N = 1 kg) = ‘F’
3. Convert mph to kmhr-1 then to ms-1 (5/8 mile = 1km )
4. Calculate vertical velocity ‘v’.
5. Power = F x v

5. Problem: A 20 tonne truck can move up a 12% gradient
at 50 mph. Calculate the truck’s power.
1. Calculate mass (1000kg = 1 tonne)
2. Calculate weight ( 10N = 1 kg) = ‘F’
3. Convert mph to kmhr-1 then to ms-1 (5/8 mile = 1km )
4. Calculate vertical velocity ‘v’.
5. Power = F x v
1. Mass = 20,000kg
2. Weight = 200,000N
3. 50mph = 8/5 x 50 kmhr = 80kmhr-1
= 80,000 / 3600 ms-1 = ms-1

6. Problem: A 20 tonne truck can move up a 12% gradient
at 50 mph. Calculate the truck’s power.
1. Calculate mass (1000kg = 1 tonne)
2. Calculate weight ( 10N = 1 kg) = ‘F’
3. Convert mph to kmhr-1 then to ms-1 (5/8 mile = 1km )
4. Calculate vertical velocity ‘v’.
5. Power = F x v
1. Mass = 20,000kg
2. Weight = 200,000N
3. 50mph = 8/5 x 50 kmhr = 80kmhr-1
= 80,000 / 3600 ms-1 = ms-1

7. Problem: A 20 tonne truck can move up a 12% gradient
at 50 mph. Calculate the truck’s power.
1. Calculate mass (1000kg = 1 tonne)
2. Calculate weight ( 10N = 1 kg) = ‘F’
3. Convert mph to kmhr-1 then to ms-1 (5/8 mile = 1km )
4. Calculate vertical velocity ‘v’.
5. Power = F x v
1. Mass = 20,000kg
2. Weight = 200,000N
3. 50mph = 8/5 x 50kmhr-1 = 80kmhr-1
= 80,000 / 3600 ms-1
= 22 ms-1
4. Vertical velocity = 22 x 12% = 2.64 ms-1
5. Power = F x v = 200,000 x 2.64
= 528 kW

8. Problem: A 20 tonne truck can move up a 12% gradient
at 50 mph. Calculate the truck’s power.
1. Calculate mass (1000kg = 1 tonne)
2. Calculate weight ( 10N = 1 kg) = ‘F’
3. Convert mph to kmhr-1 then to ms-1 (5/8 mile = 1km )
4. Calculate vertical velocity ‘v’.
5. Power = F x v
1. Mass = 20,000kg
2. Weight = 200,000N
3. 50mph = 8/5 x 50kmhr-1 = 80kmhr-1
= 80,000 / 3600 ms-1
= 22 ms-1
4. Vertical velocity = 22 x 12% = 2.64 ms-1
5. Power = F x v = 200,000 x 2.64
= 528 kW