Work Problems II
Units
Work Problems I
Power Problems I
Power Problems II
100
How much work is required to lift a 360 kilogram piano to a window whose height is 1,000 centimeters from the ground?
What is 35,280 J (360 kg x 9.8 m/s/s = 3528 N) (1000 cm / 100 = 10 m) (3528 N x 10 m = 35,280 J)
100
This is the unit for Power
Watts
100
Todd is out with his friends. Misfortune occurs and Todd and his friends find themselves getting a workout. They apply a cumulative force of 1080 N to push the car 218 m to the nearest fuel station. Determine the work done on the car.
What is 235,440 J (1080 N x 218 m)
100
A student who weighs 500 Newtons climbed the stairs from the first floor to the third floor, 15 meters above, in 20 seconds. What was his power?
What is 375 W (500 N x 15 m = 7500 J) (7500J / 20 sec = 375 W)
100
A box is pushed across the floor for a distance of 5 meters with a force of 50 Newtons in 5 seconds.
What is 50 W (50 N x 5 m = 250 J) (250 J/ 5 sec = 50 W)
200
A box rests on a horizontal, frictionless surface. A girl pushes on the box with a force of 18 N to the right and a boy pushes on the box with a force of 12 N to the left. The box moves 4.0 m to the right. Find the work done by the net force
What is 24 J (18 N - 12 N = 6 N) (6 N x 4 m = 24 J)
200
This is the unit for work.
Joules
200
Stephan and Robert push a car with a force of 2000 N over a distance of 10 m. How much work did they do?
What is 20,000 J (2000 N x 10 m)
200
If it takes 50 seconds to lift 10 Newtons of books to a height of 7 meters, calculate the power required.
What is 1.4 W (10 N x 7m = 70 J) (70 J / 50 sec = 1.4 W)
200
The power rating of an electric lawn mower is 2000 watts. If the lawn mower is used for 120 seconds, how many joules of work can it do?
What is 240,000 J (2000 W x 120 sec)
300
An 80 N force has been applied to a 30N block and move it 20 m along the direction of the force. How much work has been done to the block?
What is 2200J (80 N + 30 N = 110 N) (110 N x 20 m = 2200 J)
300
This is the unit for Force
Newtons
300
A 100 kg object is pulled vertically upward 5.0 m by a rope with an acceleration of 1.0 m/s2. Find the work done by the tension force in the rope.
What is 4,900 J (100 kg x 9.8 m/s/s = 980 N) (980 N x 5m = 4,900 J)
300
A 750 watt hairdryer is used for 60 seconds. How many joules of energy are used? Find Work!
What is 45,000 J (750 W x 60 sec = 45000 J)
300
A 500 N passenger is inside a 24500 N elevator that rises 30 m in exactly 1 minute. How much power is needed for the elevator's trip?
What is 12,500 W (24500 N + 500 N = 25000 N) (25000 N x 30 m = 750,000 J) (750,000 J/ 60 sec = answer)
400
If a group of workers can apply a force of 1000 Newtons to move a crate 20 meters using a pulley system. They pull down on the rope to lift the crate upwards. What amount of work will they have accomplished?
0 J. The direction of the force and the crate's movement are moving in opposite directions.
400
How do we calculate Newtons of force on our mass?
Mass(kg) x 9.8 m/s/s
400
During the Powerhouse lab, Jerome runs up the stairs, elevating his 102 kg body a vertical distance of 2.29 meters in a time of 1.32 seconds at a constant speed. What is his work?
What is 2,289 J (102 kg x 9.8 m/s/s = 999.6 N) (999.6 N x 2.29 m =2289 J)
400
If 360 N of force are needed to move a crate a distance of .004 km , what is the amount of work used to move the crate?
What is 1440 J (.004 km x 1000= 4m) (360 N x 4 m = 1440 J)
400

Construction workers use 1040 Newtons to move a crate 20 meters. They had 40 N of frictional resistance. What amount of work will they have accomplished?

What is 20,000 J (1040 N - 40 N = 1000 N) (1000 N x 20 m = 20,000 J)

500
If a man tries to moves a large box that weighs 10 Newtons, but the box remains stationary, how much work is being done?
0 J - no movement.
500
These are the correct units for mass and distance!
Kg and Meters
500
A 20 kg basset hound is running at an acceleration of 6m/s2 when it sees a bowls of food and stops. He ran a total distance of 12m during 2 seconds. How much work had to be?
What is 2,352 J (20 kg x 9.8 m/s/s = 196 N) (196 N x 12 m = 2352 J)
500
If 68 W of power is produced in 1.2 minutes, how much work is done?
What is 4,896 J ( 1.2 minutes x 60 sec = 72 sec) (68 W x 72 sec = 4,896 J)
500
Josh and Jake are both helping to build a brick wall which is 6 meters in height. They each lay 250 bricks, but Josh finishes this task in 3 hours while Jake requires 4.5 hours to complete his part. Who does more work, or do they both do the same amount? Who has more power? Explain.
What is same work Josh has more power because completed the same amount of work in less time.
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