Science Chapter 9 Energy
perpetual motion is impossible because...
some waste thermal energy always results from energy conversions.
All fossil fuels contain stored energy from the___________ which can be converted into other kinds of energy.
sun.
energy.
the ability to do work
Choices about energy resources depend on what 2 things.
the advantages and disadvantages of the energy resources.
potential energy
the energy an object has because of its position
chemical energy
the energy of a compound that changes as its atoms are rearranged
kinetic energy
the energy of motion
A bike is pedaled with 80 J of energy and then coasts. It does 60 J of work in moving forward until it stops. How much of the energy that was put into the bike became thermal energy?
20 J.
Describe the kinetic-potential energy conversions that occur when a basketball bounces.
Before you bounce the ball and are holding it, the basketball has potential energy because of its position. As the basketball goes down to the floor, it has kinetic energy because it is moving. For a split second when the basketball is on the floor, it has potential energy because it moved its position to the ground. When it bounces back up, it has kinetic energy because it is moving again.
Describe why chemical energy is a form of potential energy.
Chemical energy is the energy of a compound that changes as its atoms are rearranged. That means that in chemical energy there is a change in energy when its atoms are positioned differently, which is why it is a form of potential energy.
nuclear energy
Energy that comes from changes in the nucleus of an atom
How is a fossil fuel formed.
Fossil fuels are formed from the buried remains of plants and animals that lived millions of years ago.
What is the difference between kinetic and potential energy?
Kinetic energy is the energy of motion, and potential energy is the energy an object has because of its position.
How are energy and work related?
Like work, energy is expressed in joules. Energy is the ability to do work.
What is the role of machines in energy conversions?
Machines, such as the hair dryer, help harmless energy and make that energy work for you.
If someone says that a car has a high energy output, can you conclude that the car is efficient? Explain.
No because the car had to have a big amount of energy to move. A car is more efficient when a less amount of energy had to be used to move the car the same distance.
electrical energy
The energy of moving electrons
Imagine that you drop a ball. It bounces a few times and then it stops. Your friend says that the energy that the ball had is gone. Where did the energy go? Evaluate your friend's statement based on energy conversion and the conservation of energy.
The law of conservation of energy states that energy cannot be created or destroyed. The energy became stored, and it was converted into another type of energy.
A car that brakes suddenly comes to a screeching halt. Is the sound energy produced in this conversion a useful form of energy? Explain.
When a car brakes and suddenly comes to a screeching halt, the sound that is produced is not useful because when you try to stop a car using the brake, it was not made to have a sound. The sound energy does not do anything helpful.
When you hit a nail into a board by using a hammer, the head of the nail gets warm. In terms of kinetic and thermal energy, describe why you think the nail head gets warm.
When an object moves, it has kinetic energy. When you force the nail into the board, it is moving, so it has friction going into the board. Friction causes thermal energy which causes the nail head to get warm when it is getting beaten down by the hammer.
How does your body get the energy it needs?
You eat food that will give your body the energy it needs. Chemical energy comes from the food you eat. Your body uses this chemical energy to function. The chemical energy in the food you eat comes from the sun's energy. The chemical energy in the food you eat is changed into another kind of chemical energy that your body can use. Your body then uses that energy to give you kinetic energy hat you use in everything you do.
energy conversion.
a change from one form of energy to another.
Sound energy
caused by an object's vibrations
3 most common fossil fuels
coal, petroleum, natural gas
Name an energy resource that does NOT depend on the sun.
fuels used in nuclear power plants.
What happens to that potential energy after the skier races down the slope of the mountain.
it has kinetic energy because it is moving. The bottom of the hill is where the most kinetic energy is.
What two factors determine gravitational potential energy?
its weight and its height.
How to calculate mechanical energy
mechanical energy=potential energy+kinetic energy.
What is the difference between renewable and nonrenewable resources.
nonrenewable resources are some energy resources that cannot be replaced or are replaced much more slowly than they are used, and renewable resources are some energy resources that are naturally replaced more quickly than they are used.
Gasoline, wax and plastics are made from this fossil fuel
petroleum
What kind of energy does a skier have at the top of the slope?
potential energy because of his position.
Light energy
produced by the vibrations of electrically charged particles. Ex. Sun
