Download PHYSICS – UNIT 4 Study Guide. Chapter 15

Physical Science – PHYSICS – UNIT 4 Study Guide. Chapter 15 - Energy
Key Terms
Energy
Kinetic Energy
Potential
Gravitational Potential
Elastic Potential
Mechanical Energy
Thermal Energy
Chemical Energy
Electrical Energy
Electromagnetic Energy
Nuclear Energy
Energy Conversion
Conservation of Energy
Renewable Energy Resource
Nonrenewable Energy
Key Ideas
Chapter 15.1: Energy and its Forms
o Be able to describe the relationship between Energy and Work
o Know that while work is being done that energy is transferred from one object to another
o Identify and correctly use the SI unit of energy – Joules (J)
o Know the two major classifications of work – Potential and Kinetic Energy
o Know and be able to use the Kinetic Energy Equation
o Be able to calculate the gravitational potential energy of an object
o Know the difference between Elastic and gravitational potential Energy
o Know what g stands for and the number it represents (10 m/s2)
o Match the correct form of energy to different descriptions of energy
Chapter 15.2: Energy Conversion and Conservation
o Be able to describe the energy conversions of every day situations (Wind up toys, walking up
stairs, a fall object, swinging pendulum, etc.)
o Know the law of conservation of Energy and what that means for a closed system
o Be able to use the Conservation of Mechanical Energy to determine the Potential Energy, Kinetic
Energy, Speed, or height of a given object
Chapter 15.3 Energy Resources
o Know the difference between a renewable and nonrenewable resource of energy
o Be familiar with the sources of nonrenewable energy (Oil, natural gas, coal, and uranium)
o Know the sources of renewable energy (Hydroelectric, Solar, Geothermal, Biomass, Wind)
o Understand the ways that energy can be conserved
o Identify at least one way that YOU personally could conserve energy
KEY ideas from Labs
o Kinetic Energy and Mass
o Know that as the mass of a moving object is increased its Kinetic Energy is increased
o Kinetic Energy and Speed Lab
o Be able to describe how Energy, Work, and distance are related to each other
o Know that as the speed of a moving object increases, the amount of Kinetic Energy that it
has also increases
o Elasticity of a Bounce
o Know that Elasticity is a property of a material and determines how easily the material will
spring back to its original shape
o The more elastic a ball – the higher the rebound bounce
o Be able to Calculate the potential Energy of an object
o Conservation of Energy
o Observe whether or not the Mechanical Energy of a marble rolling down a ramp is
conserved, and discuss why or why not it was in the given situation.
Conceptual Practice Questions:
1. In both the Kinetic Energy & Mass and the Kinetic Energy & Speed lab, we related the amount of
Kinetic Energy that the water bottle had to the distance it moved a plastic cup. Why could we do
that?
We could relate the distance the cup moved to kinetic energy because of the fact that
Energy is the ability to do work. Work is the Force applied over a distance. We then used
the relationship that the farther the cup was pushed, the greater the work that was done.
Because energy is the ability to do work – more work done requires more energy to do that
work.
2. Explain how both mass and speed affect the kinetic energy of an object. For example – as mass is
increased what happens to the amount of kinetic energy that the object has?
As the mass of an object increases it’s kinetic energy will increase, the same is true for the
velocity – has speed increases so does the kinetic energy.
3. What is meant by the conservation of Energy?
Conservation of energy means that energy can be neither created nor destroyed – it can be
transformed or converted to a different form of energy but it will never just go away or
come out of nowhere.
4. In two of our labs, both the Elasticity of a bounce and the Conservation of Energy – we didn’t all
observe that the mechanical energy was conserved. Where did that “loss” of energy go?
We lost energy due to issues with the lab equipment, as well as the fact that there was a lot
of friction between the ramp and the ball. (the tape increased this friction). Every time the
ball bounced, some of its energy was transferred to the floor as thermal energy so the
potential energy decreased.
5. Describe the energy conversions that occur when a match is lit.
Kinetic energy (motion of the hand)  Thermal Energy (friction)  Chemical Energy
(Match starts on fire due to increase in temp)  Thermal Energy OR Electromagnetic
Energy
6. What factors determine the gravitational potential energy that an object has?
The mass of the object, the height of the object, as well as the pull of gravity on the object.
7. Can an object have both Kinetic Energy and Potential energy at the same time? Explain and give an
example to support your answer.
Yes, an object can have both. An example would be when a person is on a roller coaster
descending a hill, or on the middle of the slide, or as an object falls before it hits the
ground… there are many examples to choose from.
8. Look at the pendulum drawn below – at what point is the Gravitational Potential Energy the
greatest? The least?
The potential energy of the potential energy will be the greatest at positions A and E
provided they are at the same height. The highest point of the pendulum will have the
greatest GPE. The GPE will be the least at position C because it is at the lowest point of the
pendulum
9. Looking at the same pendulum, at what point is the kinetic energy the greatest? The least?
The kinetic will be the greatest at point C, this will be the fastest the pendulum travels, at
position B the pendulum is still accelerating, and at position D the pendulum is slowing
down. The kinetic energy will be the least at positions A and E because at that point for an
instant in time, the pendulum no longer is moving (change directions due to gravity).
10. What is the major difference between a renewable and nonrenewable resource?
The major difference is that once a nonrenewable resource is used, it is gone… or at least is
not replaced for another 1000 or even more years. A renewable resource is readily
available and does not get “used up”. For example – wind power – the wind is used to obtain
energy, but the wind is not used up.
11. What are ways that energy can be conserved? Can you give a specific example of something YOU
could do to conserve energy?
Energy can be conserved by either reducing our energy usage or making our devices more
energy efficient.
12. Decide whether the following situations are Kinetic, Potential, or Both
Situation
KE, PE, or Both
A person walking up or down the stairs
BOTH
A stretched spring
PE
An apple on a tree
PE
A ball rolling across flat ground
KE
13. What form of energy is being described below? Mechanical, Thermal, Chemical, Electrical, Nuclear,
or Electromagnetic
Description
Form of Energy
A heater is plugged into the wall and releases
Electrical (plugged in) Thermal – release of
energy in the form of heat
heat
A candle wick burns and releases both light and Chemical – the energy stored in the
heat energy
wick/candle
Boxes are lifted up into a moving vehicle
Mechanical Energy
The hydrogen atoms in the sun are fused
Nuclear Energy
together to produce heat and light
Type of Energy used in X-Ray technology
Electromagnetic
Math Practice Problems:
14. A 0.15-kg ball is dropped from the top of a 105-m building. What is the kinetic energy of the ball
when it passes the sixteenth floor at a height of 63 m? At what speed is the ball traveling at that
point?
15. A 60.0-kg person walks from the ground to the roof of a 74.8-m tall building. How much
gravitational potential energy does she have at the top of the building?
16. A pitcher throws a 0.145-kg baseball at a velocity of 30.0 m/s. How much kinetic energy does the
ball have?
17. A ball with a mass of 0.25-kg has a speed of 50 m/s just before it hits the ground. How much
kinetic energy does the ball have as it hits the ground? Assuming the ball was dropped from rest,
from what height was the ball dropped?