Transcript energy - Humble ISD

TAKS REVIEW
IPC 6
MOTION, FORCES
& ENERGY
UNITS ---- VERY IMPORTANT
In science the unit is a very important concept. The
unit identifies the measurement and can help in
working the problem.
KNOW THESE UNITS:
kg or g
- mass
L or mL - volume
m or cm - length or height
J (joule) - energy (or work) such as potential energy or KE
m/s
- velocity (speed)
m/s2
- acceleration
KNOW HOW TO SET UP A PROBLEM

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

List all the variables (parts) of the problem
WITH THE UNIT.
What is the unknown? (The answer you are
trying to find.)
Identify the equation you need and plug in
all the numbers.
Use your algebra skills to solve for your
answer.
IPC (6)
The student knows the
impact of energy
transformations in
everyday life.
The student is expected to:

6A: describe the law of
conservation of energy.
Conservation of energy

Energy (chemical, electrical, nuclear and all
kinds of energy) can be converted from one
form to another.
The food (chemical)
energy you eat is digested (converted) into the energy your
arms use to lift an axe. The axe moves up and its potential
energy increases so it can split the wood (do work on the
wood).

Energy cannot be created or destroyed.
solar energy  plant food energy  energy to move
muscles
Conservation of energy
(KE) : Problem 1
A 1-kilogram ball has a kinetic
energy of 50 joules. The
velocity of the ball is —
1. List the variables:
1 kg = mass
50 joules = energy
velocity (m/s) = ?
2. Pick the correct equation: KE = ½ mv2
3. Set up the equation:
50 joules = ½ (1 kg) v2
Use algebra to solve for v (velocity)
Solve the problem and
select the correct answer:
F
G
H
J
5 m/s
10 m/s
25 m/s
50 m/s
Problem 2
What is the potential energy of the
rock?
A 59,900 joules
B 64,600 joules
C 93,100 joules
D 121,600 joules
Problem 3
What is the approximate difference
in gravitational potential energy
of the two shaded boxes?
A 19 J
B 39 J
C 59 J
D 79 J
Problem 4
Which process best shows the conversion of
solar energy to chemical energy?
F:
G:
H:
J:
Prevailing winds causing windmills
to spin
Green plants making their own food
Uranium producing heat to make steam
Tides generating electricity
Problem 5
An inventor claims to have created an internal
combustion engine that converts 100 kJ of
chemical energy from diesel fuel to 140 kJ of
mechanical energy. This claim violates the law
of conservation of —
F: momentum
G: inertia
H: energy
J: mass
Problem 6
Only 10% of the electrical energy operating a
lightbulb is changed into visible light. Which
instrument helps identify the energy change
occurring to most of the remaining 90%?
F: Triple-beam balance
G: Thermometer
H: Magnifying glass
J: Prism
Problem 7
This experiment
probably was set
up to determine —
A: how much mechanical
energy the battery
produces
B: the pH of water during
electrolysis
C: the pressure created by an
electric current
D: how much energy is
converted to heat
Problem 8
The diagram shows an electric motor
lifting a 6 N block a distance of 3 m.
The total amount of electrical energy
used by the motor is 30 J. How much
energy does the motor convert to heat?
F
9J
G
12 J
H
18 J
J
21 J
Problem 9
Why is the sum of the products’
energy in this reaction less than
the sum of the reactants’ energy?
A
B
C
D
Energy is given off as heat.
The products absorb available energy.
Energy is trapped in the reactants.
The reactants’ energy is less than the
melting point of glucose.
The student is
expected to:

6B: investigate and demonstrate
the movement of heat through
solids, liquids and gases by
convection, conduction, and
radiation.
Heat Transfer

CONDUCTION: the transfer of energy through matter
by direct contact of particles.
This can happen in solids, liquids and gases.

CONVECTION: the transfer of energy because of the
movement of bulk masses of
particles.
This can happen only in liquids and gases - not in solids.

RADIATION: the transfer of energy by
electromagnetic waves.
Energy can move by radiation in air like the heat from your electric stove top,
or in the vacuum of space the way the Sun heats the Earth. In radiation, the
energy does not have to transfer through mass (particles).
heat transfer : Problem 10
Heat convection occurs in gases
and liquids. Heat convection does
not occur in solids because solids
are unable to —
A
B
C
D
absorb heat by vibrating
transfer heat by fluid motion
emit radiation by reflecting light
exchange heat by direct contact
Problem 11
In which container is the
substance unable to
transfer heat by convection?

Problem 12
The moon’s surface becomes hot during the
long lunar day because the sun transfers heat
to the moon. This heat transfer is
accomplished almost entirely through the
process of —
F convection
G refraction
H conduction
J radiation
Problem 13
A man who was sleeping wakes up because he
hears the smoke alarm go off in his house.
Before opening the bedroom door, the man
feels the door to see whether it is warm. He is
assuming that heat would be transferred
through the door by —
A conduction
B convection
C radiation
D compression
Problem 14
The transfer of heat by the
movement of air currents in
Earth’s atmosphere is an example
of —
A
B
C
D
conduction
convection
radiation
fusion
Problem 15
A solar heater uses energy from the
sun to heat water. The heater’s
panel is painted black to —
F improve emission of infrared radiation
G reduce the heat loss by convection
currents
H improve absorption of infrared radiation
J reduce the heater’s conducting properties
The student is
expected to:

6D: investigate and compare economic
and environmental impacts using
various energy sources such as
rechargeable or disposable batteries
and solar cells.
energy economics &
environment : Problem 16
Which of these is an advantage of producing
electricity using solar power plants rather
than using coal-fired power plants?
A Solar power plants can operate for about
10 hours per day.
B Solar power plants can produce variable
amounts of energy.
C Solar power plants produce fewer
pollutants.
D Solar power plants require continuous
sunlight.
Problem 17
Which of these devices uses the
sun’s energy directly?
A Windmill
B Hydroelectric dam
C Nuclear power plant
D Photovoltaic cell
Problem 18
A company has decided to market itself as
environmentally friendly. If the company is
going to sell calculators, the use of which
energy source would produce the fewest
by-products and the least waste?
F
Rechargeable batteries
G
Solar cells
H
Dry-cell batteries
J
Tesla coils
Problem 19
Battery-powered cars produce less air
pollution than gasoline-powered cars.
However, one environmental concern of
using battery-powered cars is that
batteries —
A
B
C
D
are heavier than gasoline engines
waste more energy than gasoline engines
contain toxic substances that are difficult
to dispose of
produce direct current rather than
alternating current
Problem 20
Which of these produces most of the
compounds responsible for causing acid
rain?
F Nuclear fission
G Fossil fuels
H Solar cells
J Windmills
Problem 21
Before 1992, in order to prevent hydrogen gas
from being produced, the zinc powder in some
alkaline batteries was covered with mercury.
Mercury is toxic to many life-forms. Which of
the following best explains how mercury from
batteries got into the environment?
A
Newly manufactured batteries were
transported long distances.
B
Operating batteries increased the
temperature of conductors.
C
Used batteries discarded in landfills
decomposed.
D
Voltage loss occurred between battery
terminals.

Problem 22
In West Texas and Southern California, high
winds drive turbines that generate electricity.
One advantage that wind energy has over
energy generated from solar cells is that wind
energy —
A
 B
C
D
is plentiful everywhere
can be generated at night
produces cleaner energy
is free of environmental hazards
The student is expected to:

6F: investigate and compare
series and parallel circuits.
circuits


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You need three things for a complete circuit. (1) A battery (or
other power source), (2) a wire and (3) something to convert the
electrical energy into some other energy form (like a light bulb or
a hair dryer).
A complete circuit must make a complete “circle”. You must be
able to trace the circuit from the positive end of the battery all
the way around to the negative end without a break.
Ohm’s Law relates current to voltage and resistance.
I=V
V = voltage in Volts (V)
R
I = current in Amps (A)
R = resistance in ohms (W)
PARALLEL AND SERIES CIRCUITS
SERIES CIRCUIT – all the parts of the circuit
come one after the other. There is only one path
for the current to follow.
 PARALLEL CIRCUIT – there are branches in
the circuit which allow the current to flow in
different pathways.

circuits : Problem 23
Which switch, if opened, will cause
the lightbulb to stop glowing?
F:
G:
H:
J:
Q
R
S
T
Problem 24
What is the current in a copper wire
that has a resistance of 2 ohms
and is connected to a 9-volt
electrical source?
F
0.22 amp
G 4.5 amps
H 11.0 amps
J
18.0 amps
Problem 25
How much current is flowing
through this circuit?
A 0.32 A
B 3.1 A
C 4.0 A
D 12.5 A
Problem 26
Which circuit is built
so that if one light bulb
goes out, the other three
light bulbs will continue
to glow?
Let’s do a little more –
Which circuit is built so that NONE of the bulbs
will glow? WHY?
Which circuit is built so that ONE of the bulbs will
glow? WHY?
Which circuit is built so that ALL of the bulbs will
glow but if one goes out, the other three
will also go out? WHY?
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