MOTION, FORCES & ENERGY TAKS REVIEW IPC 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 - volume m or cm - length or height J (joule) - energy (or work) such as potential energy or KE m/s - velocity (speed) m/s 2 - 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 mv 2 3. Set up the equation: 50 joules = ½ (1 kg) v 2 Use algebra to solve for v (velocity)

Solve the problem and select the correct answer: F 5 m/s G 10 m/s H 25 m/s J 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: Prevailing winds causing windmills to spin G: Green plants making their own food H: Uranium producing heat to make steam J: 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 9 J 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 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: the transfer of energy through matter CONDUCTION: the transfer of energy through matter by direct contact of particles. by direct contact of particles. This can happen in solids, liquids and gases. CONVECTION: the transfer of energy because of the CONVECTION: the transfer of energy because of the movement of bulk masses of movement of bulk masses of particles. particles. This can happen only in liquids and gases - not in solids. RADIATION: the transfer of energy by 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

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 vibrating B transfer heat by fluid motion C emit radiation by reflecting light D exchange heat by direct contact

Problem 11 In which container is the substance unable to transfer heat by convection? 

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 12

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 conduction B convection C radiation D 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 are heavier than gasoline engines B waste more energy than gasoline engines C contain toxic substances that are difficult to dispose of D 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 is plentiful everywhere B can be generated at night C produces cleaner energy D 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 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). 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. 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. Ohm’s Law relates current to voltage and resistance. I = VV = voltage in Volts (V) RI = current in Amps (A) RI = 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: Q G: R H: S J: 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? A0.32 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?