Download Energy – Study Guide

Energy – Study Guide (37 points total) – Due Nov. 5
***Note: late review guides receive ½ credit ***
Name ________________________
1. Define these words. (0.5 pts each – 6 pts total)
Energy – The ability to do work.
Mechanical Energy – The energy associated with the motion or position of everyday objects.
Thermal/Heat Energy – The total KE/GPE of the vibrations of the particles in an object.
Chemical Energy – Energy stored in chemical bonds.
Electromagnetic Energy – Energy consisting of changing electric and magnetic fields (otherwise
known as “light”)
Nuclear Energy – The energy stored in the nucleus of an atom.
Kinetic Energy – Energy an object has due to its motion.
Potential Energy – Energy that is stored as a result of position or shape.
Gravitational Potential Energy – Potential energy that depends on an object’s height.
Conservation of Energy – Finding ways to use less energy or use it more efficiently.
Work – Force applied over a distance (force * distance).
Power – The rate of doing work (work/time).
2. Fill-in. (0.5 pts each – 8 pts total)
A ______JOULE_____ is a measure of energy.
Mechanical energy is associated with ____MOTION______.
Electromagnetic energy is associated with the motion of ____MOVING___ __ELECTRONS____.
Heat energy is associated with the ____SPEED___ that atoms and molecules move.
Chemical energy is energy that _______BONDS___ atoms together.
Nuclear energy is what holds the _____NUCLEUS____ of an atom together.
Kinetic energy varies with the _____MASS____ and _____VELOCITY____ of an object.
Gasoline is an example of stored ____CHEMICAL______ energy.
The factor that has the greatest effect on kinetic energy is ____VELOCITY (it is squared)______.
_____ENERGY____ is the ability to do work.
The energy of position is called ____POTENTIAL____ energy.
Gravitational potential energy is equal to ___WEIGHT____ times _____HEIGHT____.
The __JOULE___ is the unit of work. It is also equal to 1 newton-meter.
The unit of power is called the _____WATT____.
A watt is equal to ___1__ J/sec
1000 watts would be called 1 __KILOWATT___.
3. Short Answer. (1 points. each – 4 points total)
Explain why no work is done when you push against a wall.
There is no distance moved, hence force X distance will be equal to zero.
Who does more work, a boy coasting on his bike down a hill, or a girl picking up a piece of paper off
of the floor?
The girl picking up the paper. She exerts an upward force on the paper and moves it a
distance. The boy on the bike does no work, as he is not exerting any force.
A 900-N mountain climber climbs a 100 meter cliff, how much did he work?
W =F*d
= 900 N * 100 m
= 90,000 N*m = 90,000 J
If you do 4000 joules of work in 20 seconds, how much power do you have?
P
= W/t
= 4000 J/20 s
= 200 J/s
= 200 watts
4. Energy Resources. (1 pt each – 10 pts total)
Which energy sources currently account for most of the world’s energy use?
Fossil (Non-renewable) Fuels:
Coal
Oil (petroleum)
Natural Gas
And also
Uranium
Where do most non-renewable energy sources originate?
Inside the earth or near Earth’s surface.
Why are coal, oil, and natural gas considered to be nonrenewable resources?
They are being consumed much faster than they are being produced.
How do non-renewable energy resources differ from renewable energy sources?
Renewable energy resources can be replaced in reasonable short periods of time.
What are some advantages and disadvantages of the following types of renewable energy resources?
ADVANTAGES
DISADVANTAGES
Solar
High Energy, Easy to install/move,
Long-lasting, Low Env. Impact
Sun can be blocked, low efficiency,
Backup system, expensive, High land use
Wind
No pollution, Low cost, safe
Wind-dependent, disrupts migration
Disrupts local wind patterns
Hydro
Low-cost electricity, wide availability
Cost, environmental impacts, pollution,
Loss of biodiversity, Invasive species
5. Potential – Kinetic Energy. (1 pt each – 5 pts total)
The diagram below shows a pendulum in various stages of one swing. Compare the kinetic and
potential energy of the pendulum at each labeled point in its swing.
Point A:
KE
Minimum
PE
Maximum
Point B:
Gaining KE
Losing GPE
Point C:
Maximum KE
Minimum GPE
Point D:
Losing KE
Gaining GPE
Point E:
Minimum
Maximum
6. Energy Calculations. (1 pts each – 4 pts total)
GPE = weight X height
KE = ½ mv2
GPE
w
KE
h
½ m v2
What is the height of an object that weighs 490 N if its G.P.E. is 4900 N-m?
GPE = w * h, so….
h = GPE/w
h = 4900 N-m/490 N
h = 10 m
What is the kinetic energy of a 50-kg mass that is moving with a velocity of 10 m/sec?
KE = ½ mv2
KE = ½ (50 kg)(10 m/s)2
KE = 2500 J
A baseball that has a mass of 0.4 kg is thrown so that it attains a velocity of 18 m/sec. What is the
kinetic energy of the ball at that velocity?
KE = ½ mv2
KE = ½ (0.4 kg)(18 m/s)2
KE = 64.8 J
A 0.49-kg squirrel jumps from a tree branch that is 3.6 m high to the top of a bird feeder that is 1.5 m
high. What is the change in gravitational potential energy of the squirrel? (The acceleration due to
gravity is 9.8 m/s2, w = m g)
GPE = w * h
But, we do not know the weight yet, nor do we know how much
the height changed. So…..
w = m*g
w = 0.49 kg * 9.8 m/s2
w = 4.8 Newtons
Change in height = 3.6 m – 1.5 m = 2.1 m
Now GPE = w * h
= 4.8 N * 2.1 m
= 10.1 J