Energy
Power
Work
Misc
100
Energy in motion is known as:
Kinetic Energy
100
Power is measured in what unit?
Watts (W)
100
Work is measured in which unit?
Joules (J) is the correct unit work. It is equivalent to 1 N*m
100
What is the kinetic energy of a 0.500 kg toy car moving at a rate of 1.50 m/s?
KE = 1/2mv2
1/2 * 0.500 kg * (1.50 m/s)2 = 0.563 J
200
A 1500 kg beam is held 50 meters in the air by a crane. What is the potential energy of the beam?
PE = mgh
1500 kg * 9.8 m/s/s * 50
735,000 J of Potential Energy
200
1 Horsepower is equivalent to roughly 746 Watts. How many horsepower does an 1100 Watt microwave have?
1100 watt divided by 746 watts/horsepower = 1.48 Horsepower
200
Mr. Moyers’ class was studying how work is done on an object. In which
situation is the amount of work done on the object equal to zero?
A. A shopper pushes a cart with a broken wheel.
B. An apple growing on a tree falls to the ground.
C. A person pushes on a heavy box but is unable to move it.
D. An athlete swings a bat in the air without hitting anything.
C. A person pushes on a heavy box but is unable to move it.
W = F*d. The distance would be 0 since the box didn't move meaning no work was done.
200
Peter does 3,000 joules (J) of work by moving an object 40 meters (m). What is the force that Peter applies to the object?
W = F * d, when re-arrange to solve for Force,
F = W/d.
3000 J /40 meters =75 N of Force
300
A 1000 kilogram roller coaster car has 490000 Joules of potential energy at the very top of a 50 meter tall roller coaster hill. How much kinetic energy will the roller coaster have when it descends to the very bottom of the hill?
490,000 J.
Remember that energy is not lost or conserved, but transferred back and forth. At the top of the hill an object has all potential energy, at the bottom, it has all kinetic energy as there is 0 height.
300
A phone car charger requires 120 Joules ever 24 seconds in order to charge the phone. What is the power the charger requires?
5 Watts.
Power = work/time (120/24 seconds)
300
Calculate the work done to push the box 3.0 meters with a force of 500 N.
1500 J of Work
300
A forklift lifts 5 boxes from the ground to a height of 2 meters (m). The boxes push down with a force of 1000 newtons (N). How much work was done by the forklift to lift the boxes?
W = F*D
1000 N * 2 m = 2000 J
400
A 4.5 kg remote control car collides into a wall at 13.5 m/s. What is the kinetic energy of the car?
KE = 1/2mv2
1/2 * 4.5 kg * (13.5 m/s)2 = 410 J of Kinetic energy
400
An 13 Watt LED lightbulb produce 46,800 J of Work every 3600 seconds (1 hour). How long in seconds will a 40 Watt light bulb stay on if it produces the same amount of work?
Power = Work/time...when re-arranged you'll get
time = work/power
46,800 J of Work/40 Watt Light Bulb = 1170 seconds (19.5 minutes)
400
Two people applied 100 N of force each to move a bookcase 3 m. How much work was done on the bookcase?
W = F*d
W = 200 N * 3 N
W = 600 J
400
What is the height of a cliff jumper who has a mass of 62 kg, and 21,300 J of Potential Energy?
PE = mgh. You need to re-arrange for height, meaning that h = PE/mg
21,300 J / (62 kg * 9.8 m/s/s) = 35.06 meters high
500
A truck traveling at 31.4 m/s has a mass of 1020 kg. A 850 kg car gets in the fast lane and passes the truck as it is traveling at 35.2 m/s. Which vehicle has more kinetic energy?
The car has more kinetic energy.
Truck = 1/2 * 1020 * 31.42 =502,839.6 J
Car = 1/2 * 850 * 35.22 = 526,592 J
500
Sammy uses a pulley to hoist a crate 10 meters high in 5 seconds. Sammy applies 980 N of force to hoist the crate. Calculate the amount of power Sammy expended.
1960 Watts
Power = work/time
work = force * distance (980 N *10 m)
Once you solve for work, 9800 J, you can plug it into the power equation and divide by the 5 seconds.
500
Which Cart produced the most work?
Cart W with 10 J of Work
500
A 600-newton person runs up a set of stairs that is 2.5 meters high in 2 seconds. How much power has the person generated?
P = Work / time and W = F*d
You must first solve for Work....W = 600N*2.5m = 1500 J
Power = Work/Time 1500 J/2 seconds = 750 Watts