Which requires the LEAST amount of work: Pushing on a car with 1000N of force, but the car doesn't move. Pushing on a piece of paper with .01N of force, but the paper moves 10cm, or pushing on a car with 500N of force to make it move 1m.
1000N with no motion. NO MOTION = NO WORK.
100
Which of the following statements about work is FALSE: Energy can be used to do work. Energy can be transformed. Energy is the same as power. Energy and work have the same units.
Energy is the same as power.
100
True or false: A machine reduces the amount of work that needs to be done.
False
100
What is the amount of power if you have done 200J of work in 4s?
Power = work/time
50 W = 200J/4s
100
What kind of simple machines are all sharp things?
Wedge
200
What is the unit of work and energy?
Joule
200
Where does a ball have the most kinetic energy as it rolls down a hill: at the top or the bottom? Why?
At the bottom. Kinetic energy is energy of motion. The faster an object moves, the more kinetic energy it has.
200
Name two simple machines that are just fancy inclined planes.
Wedge and screw.
200
What is the mechanical advantage of a lever that allows you to lift 300N of weight with only 50N of input?
MA = Output force/input force
6 = 300N/50N
200
Explain how you can increase your gravitation potential energy.
Increase height, increase mass, or increase the amount of gravity on the objects.
300
What is the unit of power?
Watt
300
What are the 3 parts of gravitational potential energy?
Mass, height, and acceleration due to gravity
300
What do we call a machine that is composed of two or more simple machines put together?
Compound machine
300
What is the Gravitational potential energy of a 2kg rock that is 1m above the ground on Earth?
GPE = mass x acceleration due to gravity x height
19.6J =2kg x 9.8m/s/s x 1m
300
Which would make a bigger change in kinetic energy, doubling the mass or doubling the velocity? Why?
Doubling the velocity. The velocity is squared when you use the kinetic energy formula. So doubling velocity would actually quadruple the kinetic energy.
400
What do we call the rate at which work is done?
Power
400
What form of energy does gasoline have: heat, light, nuclear, chemical, or electricity?
Chemical
400
If a machine multiplies the force, what do you usually give up? Hint: If you win with force, you lose with____.
Distance
400
If a 2kg book is thrown through the air with 3m/s velocity, what is its kinetic energy?
KE = 1/2 mass (velocity)^2.
9 J =1/2 (2kg) (3m/s)^2
400
Can you have an inclined plane with a mechanical advantage less than 1? Why or why not?
MA = input distance / output distance. You cannot have a ramp that is shorter than it is tall, because it would not touch the ground.
500
What is one way to increase your power, regarding the amount of work you do or the amount of time it takes.
Do more work in the same amount of time.
Do the same amount of work faster
500
What form of energy is released when two hydrogen atoms on the sun fuse together to form a helium atom?
Nuclear
500
What kind of theoretical machine would have 100% efficiency? What force prevents this machine from existing
Perpetual motion machine. Friction
500
What is the efficiency of a machine that does 18 J of work for every 24 J of energy you put into it?
75%
500
Explain WHY you have done no work, if the object you are exerting force on doesn't move.
Work = force x distance. If your distance is 0m, you haven't moved the object. No matter how large the force is, anything times 0 is 0, and so work is 0J.