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Amy uses 20N of force to push a lawn mower 10 meters. How much work does she do?

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Presentation on theme: "Amy uses 20N of force to push a lawn mower 10 meters. How much work does she do?"— Presentation transcript:

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2 Amy uses 20N of force to push a lawn mower 10 meters. How much work does she do?

3 Amy uses 20N of force to push a lawn mower 10 meters. How much work does she do? W = F X D = 20 N X 10 M = 200 NM = 200 JOULES

4 Frank does 2400J of work in climbing a set of stairs that is 7 m high. What force does Frank exert when he climbs the stairs?

5 Frank does 2400J of work in climbing a set of stairs that is 7 m high. What force does Frank exert when he climbs the stairs? W = F X D = 2400 J = F X 7M F = 2400/7 = 343 NEWTONS

6 How much power is required to pull a sled if you use 60J of work in 5 seconds?

7 How much power is required to pull a sled if you use 60J of work in 5 seconds? POWER = W/T = 60/5 = 12 WATTS

8 How much work does an elephant do while moving a circus wagon 20 meters with a pulling force of 200N?

9 How much work does an elephant do while moving a circus wagon 20 meters with a pulling force of 200N? W = F X D = 200 X 20 = 4000 JOULES

10 If it takes 5 seconds for you to do 1000J of work, what is your power output?

11 If it takes 5 seconds for you to do 1000J of work, what is your power output? POWER = W/T = 1000/5 = 200 WATTS

12 A 900N mountain climber scales a 100m cliff. How much work is done by the mountain climber?

13 A 900N mountain climber scales a 100m cliff. How much work is done by the mountain climber? WORK = FORCE X DISTANCE = 900 N X 100 m = 90,000 watts

14 A small motor does 4000J of work in 20 seconds. What is the power of the motor in watts?

15 A small motor does 4000J of work in 20 seconds. What is the power of the motor in watts? POWER = WORK/TIME = 4000/20 = 200 WATTS

16 A woman runs a kilometer using a force of 210N and a power output of 500W. How long in minutes does it take this woman to complete 1 kilometer?

17 A woman runs a kilometer using a force of 210N and a power output of 500W. How long in minutes does it take this woman to complete 1 kilometer? WORK = FORCE X DISTANCE = 210 N X 1000m = 210,000 JOULES POWER = WORK/TIME TIME = WORK/POWER = 210,000/500 = 420 sec = 7 min

18 A toy cart moves with a kinetic energy of 30 J. If its speed is doubled, what will its kinetic energy be? SINCE KE = ½ mv 2 IF V IS DOUBLED, KE WILL INCREASE BY A FACTOR OF 4, SO KE = 120 J

19 A 70 kg diver is standing on a 10 m tower. What is the potential energy of the diver?

20 A 70 kg diver is standing on a 10 m tower. What is the potential energy of the diver? WEIGHT OF DIVER = 70 X 9.8 = 686 N PE = 686 X 10 = 6860 J

21 The 70 kg diver steps off the tower and falls into the water. What is the kinetic energy of the diver? 6860 J

22 A 1300-kg car coasts on a horizontal road with a speed of 18 m/s. What is the kinetic energy of the car? KE = ½ mv 2 = ½ x 1300 x (18) 2 = J = KJ

23 When the 1300 kg car comes to a stop, what is its potential energy?

24 When the 1300 kg car comes to a stop, what is its potential energy? IT IS ON A HORIZONTAL ROAD. IT HAS NO HEIGHT ABOVE THE GROUND, SO THE POTENTIAL ENERGY IS ZERO.

25 What is the speed of a 3700 kg car if it has a kinetic energy of 118,400 J?

26 What is the speed of a 3700 kg car if it has a kinetic energy of 118,400 J? KE = ½ mv 2 v 2 = 2 x KE/m = 2 x /3700 = 64 v = 8 m/s


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