MOTION, FORCES

& ENERGY

TAKS REVIEWIPC 6

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 - volumem or cm - length or heightJ (joule) - energy (or work) such as potential

energy or KE m/s - velocity (speed)

m/s2 - acceleration

KNOW HOW TO SET UP A PROBLEM

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 5 m/sG 10 m/sH 25 m/sJ 50 m/s

Problem 2

What is the potential energy of the rock?

A 59,900 joulesB 64,600 joulesC 93,100 joulesD 121,600 joules

Problem 3

What is the approximate difference in gravitational potential energy of the two shaded boxes?

A 19 JB 39 JC 59 JD 79 J

Problem 4

Which process best shows the conversion of solar energy to chemical energy?

F: Prevailing winds causing windmills to spinG: Green plants making their own foodH: Uranium producing heat to make steamJ: Tides generating electricity

Problem 5

An inventor claims to have created an internalcombustion engine that converts 100 kJ ofchemical energy from diesel fuel to 140 kJ ofmechanical energy. This claim violates the lawof conservation of —F: momentumG: inertiaH: energyJ: 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 balanceG: ThermometerH: Magnifying glassJ: Prism

Problem 7This experiment

probably was set up to determine —

A: how much mechanical energy the battery producesB: the pH of water during electrolysisC: the pressure created by an electric currentD: 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 9 JG 12 JH 18 JJ 21 J

Problem 9

Why is the sum of the products’ energy in this reaction less than the sum of the reactants’ energy?

A Energy is given off as heat.B The products absorb available energy.C Energy is trapped in the reactants.D 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.

CONDUCTION: CONDUCTION: the transfer of energy through the transfer of energy through mattermatter

by by direct contactdirect contact of particles. of particles.This can happen in solids, liquids and gases.This can happen in solids, liquids and gases.

CONVECTION: CONVECTION: the transfer of energy because of the transfer of energy because of thethe

movement of movement of bulk massesbulk masses of of particles.particles.

This can happen only in liquids and gases - not in solids.This can happen only in liquids and gases - not in solids.

RADIATION: RADIATION: the transfer of energy by the transfer of energy by electromagnetic waves. electromagnetic waves.

Energy can move by radiation in air like the heat from your electric 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. 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 In radiation, the energy does not have to transfer through mass (particles).(particles).

Heat Transfer

heat transfer : Problem 10

Heat convection occurs in gases and liquids. Heat convection does not occur in solids because solids are unable to —

A absorb heat by vibratingB transfer heat by fluid motionC emit radiation by reflecting lightD exchange heat by direct contact

Problem 11

In which container is the substance unable totransfer heat by convection?

The moon’s surface becomes hot during thelong lunar day because the sun transfers heatto the moon. This heat transfer isaccomplished almost entirely through theprocess of —

F convectionG refractionH conductionJ radiation

Problem 12

Problem 13A man who was sleeping wakes up because hehears the smoke alarm go off in his house.Before opening the bedroom door, the manfeels the door to see whether it is warm. He isassuming that heat would be transferredthrough the door by —

A conductionB convectionC radiationD compression

Problem 14

The transfer of heat by the movement of air currents in Earth’s atmosphere is an example of —A conductionB convectionC radiationD 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 radiationG reduce the heat loss by convection

currentsH improve absorption of infrared radiationJ 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 producingelectricity using solar power plants ratherthan 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 WindmillB Hydroelectric damC Nuclear power plantD Photovoltaic cell

Problem 18

A company has decided to market itself asenvironmentally friendly. If the company isgoing to sell calculators, the use of whichenergy source would produce the fewestby-products and the least waste?

F Rechargeable batteriesG Solar cellsH Dry-cell batteriesJ Tesla coils

Problem 19

Battery-powered cars produce less airpollution than gasoline-powered cars.However, one environmental concern of

using battery-powered cars is that batteries —A are heavier than gasoline enginesB waste more energy than gasoline enginesC contain toxic substances that are difficult

to dispose ofD produce direct current rather than

alternating current

Problem 20

Which of these produces most of thecompounds responsible for causing acidrain?

F Nuclear fissionG Fossil fuelsH Solar cellsJ Windmills

Problem 21

Before 1992, in order to prevent hydrogen gasfrom being produced, the zinc powder in somealkaline batteries was covered with mercury.Mercury is toxic to many life-forms. Which ofthe following best explains how mercury frombatteries 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, highwinds drive turbines that generate electricity.One advantage that wind energy has overenergy generated from solar cells is that windenergy —

A is plentiful everywhere B can be generated at night

C produces cleaner energyD is free of environmental hazards

The student is expected to:

6F: investigate and compare series and parallel circuits.

circuits You need three things for a complete circuit. (1) A You need three things for a complete circuit. (1) A

battery (or other power source), (2) a wire and (3) battery (or other power source), (2) a wire and (3) something to convert the electrical energy into some something to convert the electrical energy into some other energy form (like a light bulb or a hair dryer).other energy form (like a light bulb or a hair dryer).

A complete circuit must make a complete “circle”. A complete circuit must make a complete “circle”. You must be able to trace the circuit from the You must be able to trace the circuit from the positive end of the battery all the way around to the positive end of the battery all the way around to the negative end without a break.negative end without a break.

Ohm’s Law relates current to voltage and resistance.Ohm’s Law relates current to voltage and resistance.

I = I = VV V = voltage in Volts (V)V = voltage in Volts (V)

RR I = current in Amps (A)I = current in Amps (A)

R = resistance in ohms (W)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: QG: RH: SJ: 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 ampG 4.5 ampsH 11.0 ampsJ 18.0 amps

Problem 25

How much current is flowing through this circuit?

A 0.32 AB 3.1 AC 4.0 AD 12.5 A

Problem 26

Which circuit is built so that if one light bulbgoes out, the other threelight bulbs will continueto 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?