Chapter 9 Study Guide
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Introduction to Energy Study Guide – Part 1
1. What is energy?
The ability to do work
2. What is kinetic energy?
The energy of motion (movement)
3. Can objects with kinetic energy do work? Give an example.
Yes. If you swing a hammer, you can do the work of driving a nail into a board.
4. What two things does kinetic energy depend on (in other words, what two things do you need to know to calculate kinetic energy?)
The object’s mass and its speed. Speed is the more important one of the two.
5. If two bicycles have the same mass, but one is traveling at 10 m/s and the other is traveling at 15 m/s, which has more kinetic energy?
The faster one
6. If two people are running at the same speed, but one has a mass of 60 kg and the other has a mass of 75 kg, which has more kinetic energy?
The more massive one
7. What is potential energy?
Potential energy is stored energy 8. What does it mean when we say potential energy depends on the height of the object? Give an example and illustrate it.
Gravitational potential energy is the energy something has because of its height above the earth. A can of beans, dropping from 200 feet, will hit with more force, because it had more energy than a can of beans dropping from 6 inches.
9. What does it mean when we say potential energy depends on the shape of an object? Give an example.
If you do work on an object so that the shape changes, you can give it potential energy. For instance, when you pull back the string of a bow, you do work on it to change its shape. The energy you used is transferred to the bow, stored there, and then used to give energy to the arrow.
10. At which point does this pendulum have the most KE?
At which point does the pendulum have the most PE? Point #1
At point 4, what is happening to the KE and PE?
At point 4, the PE is increasing, while the KE is decreasing 11.Draw a pendulum, and show how the potential energy and kinetic energy change as it swings.
1. Highest potential energy when you first let it go.
3. At the other side, the potential energy is high again, and the kinetic is low. +KE -KE - PE +PE
2. When the pendulum hits the middle, its KE is at its highest.
12. What is an energy conversion?
A change from one form of energy to another.
13.Show how we would use symbols to describe the energy conversions that take place in the following machines:
mechanical alarm clock electrical light
sound thermal
battery chemical electrical thermal light bulb electrical light
thermal
mechanical thermal blender electrical kinetic
sound
14.What is the law of conservation of energy?
Says that energy can neither be created nor destroyed. It just gets converted from one form to another.
15.Whenever an energy conversion takes place, one form of energy is always created. What form is that?
Thermal energy is produced with every conversion.
16.Where does the thermal energy from energy conversions go?
Most of it goes into the air.
17.Is it possible to have a machine that keeps moving forever without any source of energy? Why or why not?
No, because, remember, energy cannot be created. Therefore, every machine in the world has to have some source of energy.