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Power is: The rate of doing work.

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Presentation on theme: "Power is: The rate of doing work."— Presentation transcript:

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

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