Year 9 End of Year Physics Study Plan.pdfView Download

PHYSICS STUDY PLAN

FOR YEAR 9 FINAL

EXAMINATION

GJ Zahra, B.Ed (Hons)

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

1

Study Guide ... 2

General Tips ... 2

Part 1: General ... 2

Part 2: Density ... 2

Part 3: Forces... 2

Part 4: Hooke’s Law ... 3

Part 5: Moments ... 3

Part 6: Pressure ... 3

Part 7: Work, Energy and Power ... 3

Part 8: Energy Sources... 3

Part 9: Heat ... 4

Part 10: Earth and the Universe ... 4

Revision Questions ... 5

Units and Measurements ... 5

Density ... 5

Forces ... 5

Hooke’s Law ... 6

Moments ... 6

Pressure ... 7

Work, Energy and Power ... 7

Energy Sources ... 8

Heat ... 8

Earth and the Universe ... 8

Model Answers to Questions ... 9

Units and Measurements ... 9

Density ... 9

Forces ... 10

Hooke’s Law ... 10

Moments ... 11

Pressure ... 12

Work, Energy and Power ... 13

Energy Sources ... 13

Heat ... 13

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

2

Study Guide

General Tips

Reading the notes is never enough to do well in an exam. It is important to understand and question what is being read. It is also very important to use and apply the newly acquired information. While reading the notes, try to change the notes into your own words, draw flowcharts, pictures or any other thing that you find useful, according to your own learning style. After having understood the notes, work out the questions that were completed throughout the year: these questions in the worksheets are typical exam questions!

Studying is best done bit by bit at regular intervals, rather than trying to study whole chunks at one go. Timetabling your studies is not just more efficient for studying purposes, but also leaves you with more extra time to enjoy yourself with a variety of activities.

Your annual exam will be a SEC Paper 1 standard exam. It will have ten questions carrying 10 marks each. The fifth question is always about graph skills and includes plotting and using a graph which you may or may not have plotted. Your practical work will carry 15% of your final mark.

Part 1: General

 Which are the SI units? How can one convert to SI units? What does each prefix (kilo, centi, mega, nano, etc) mean?

 Which are the instruments used to measure length, time, volume, mass and temperature? What precautions must be taken when using each piece of equipment?

 Students are expected to produce plans, diagrams and precautions related to experiments carried out during the year. Do not memorize whole chunks of methods – rather learn to plan these out by knowing what needs to be measured!

 Graph plotting. Be able to calculate the gradient of a straight line graph. Understand that a straight line graph shows direct proportionality.

Part 2: Density

 Define density and be able to explain how it varies with mass, volume and temperature.  Use the equation for density and be able to rearrange it to find any missing property.  Floating and sinking as related to density.

 Students are expected to know that the density of water is 1g/cm3 or 1,000kg/m3.

Part 3: Forces

 Draw force diagrams and explain terms like resultant force and equilibrium using these diagrams. Calculate resultant forces from diagrams and state that these cause acceleration (change in the object motion).

 Define centre of gravity.

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

3

Part 4: Hooke’s Law

 Define Hooke’s law.

 Understand and use terms like directly proportional, elastic limit, denatured and stiff/soft.  Sketch force vs extension graphs for an object that obeys Hooke’s law (before and after it’s

elastic limit) and compare graphs for springs with different stiffness.

Part 5: Moments

 Define a moment as the turning effect of a force.

 Use the equation Moment = Force x distance. Students are expected to remember this equation (i.e. it will not be provided).

 Recall the law of moments. Use this law to calculate a missing force or distance.

Part 6: Pressure

1. Define pressure and state its units.

2. Use the equation P = F/A for pressure in solids or that applied in hydraulic machines. Use this equation to predict how pressure will change with changes in force and/or area. 3. Use the equation P = ρgh for pressure in liquids and use this equation to predict how the

pressure will change with changes in density, acceleration due to gravity or height. 4. Use the law of hydraulics to predict the pressure in a hydraulic fluid and then use the

equation P = F/A to calculate an unknown force or area at a secondary piston.

5. Predict and explain the correlations between pressure, temperature, density and volume.

Part 7: Work, Energy and Power

6. State and apply the principle of conservation of energy. Draw energy transfer diagrams and identify energy losses in particular systems

7. Define and calculate work using the equation Work = force x distance moved in the direction of the force

8. Calculate potential and kinetic energy using the equations PE = mgh and KE = ½ mv2 respectively

9. Relate PE, KE and total mechanical energy for a free falling body or an oscillating body 10. Define power as the rate of doing work and calculate it using the equation P = E/t 11. Calculate the percentage efficiency of a system

Part 8: Energy Sources

1. Recall several energy sources together with their advantages and disadvantages 2. Define renewable and non-renewable sources of energy

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

4

Part 9: Heat

1. State that heat is a form of energy measured in Joules

2. Use the theory of particles to explain expansion and contraction

3. Use the theory of particles to explain how energy can be transferred by conduction, convection and radiation

4. Define specific heat capacity and use the equation H = mcΔT

5. Black as a good absorber and emitter of heat as opposed to white/silver which is a bad absorber and emitter of heat

6. Apply knowledge about heat transfer, specific heat capacity and absorbers and emitters of heat to explain the choice of different materials in given situations

Part 10: Earth and the Universe

1. Recall that the force of gravity is the force that keeps lighter objects orbiting heavier ones 2. Use the heliocentric (sun at the centre) model to explain the following phenomena: day and

night; year; seasons

3. Define a planet and use this definition to classify given objects (e.g. Pluto) as planets or not 4. Distinguish between moons, planets, stars, galaxies and the universe

5. By being given the order of planets from the sun, explain the observed variations in temperature and year length

6. Recall some benefits of space exploration

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

5

Revision Questions

Units and Measurements

1. What are the SI units used to measure: a. Distance?

b. Time? c. Density? d. Mass? 2. Convert to SI units:

a. 200g b. 25cm3 c. 2:15 hours d. 2.5 g/cm3

3. What is the apparatus used to measure a. The volume of some water b. The volume of a wooden door

4. For each apparatus mentioned in 3, give two precautions.

Density

1. An iron door has a volume of 2m x 1.2m x 10cm.

a. Calculate the mass of the door if the density of iron is 7,870 kg/m3.

b. Predict, giving reasons, whether the door will float on each of the following liquids: i. Water (density = 1,000 kg/m3)

ii. Mercury (density = 13,000 kg/m3)

2. Hot air balloons heat the air inside the balloon so that the balloon can rise. Explain using the theory of particles why hot air is less dense than cold air.

Forces

1. What is the difference between scalar and vector quantities? 2. An astronaut weighs 800 N on Earth. Give:

a. The mass of the astronaut on Earth (g = 10 m/s2) b. The mass of the astronaut in outer space

c. The weight of the astronaut in outer space

d. The weight of the astronaut on the moon (g = 1.6 m/s2) 3. Draw and label the forces acting on a

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

6

Hooke’s Law

1. State Hooke’s Law

2. From the graphs below choose

a. The force-extension graph for a material that obeys Hooke’s Law

b. The force-extension graph for a material that does not obey Hooke’s Law c. The force-extension graph for a material that has exceeded its elastic limit

3. From the sketch below, showing the force-extension relationship of two different helical springs, choose the spring that is the stiffest.

Moments

1. Define

a. Centre of gravity b. Moment

2. A uniform metre rule is balanced from its 50cm mark on a pivot. A weight of 3.5N is placed on the 20cm mark while an object of unknown weight is placed on the 65cm mark when the ruler is in equilibrium.

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

7

Pressure

1. Define pressure

2. Stefan of mass 55kg sits on a chair of mass 5kg having four legs each of base area 0.04m x 0.04m.

a. Calculate the total downward force

b. Calculate the total area of contact of the chair with the ground c. Calculate the pressure exerted by the system on the ground

d. Stefan’s mother is constantly refraining Stefan from swinging on the chair’s back legs because she says this can damage their parquet floor. Explain the physics behind the statement.

3. A scuba diver went to visit the sunken British Destroyer in Marsamxett Harbour. The ship lies approximately 16m under water. The atmospheric pressure of the day was 101,325 Pa. Calculate the total pressure acting on the scuba diver at this depth (density of sea water is 1,150 kg/m3).

4. Draw a diagram to describe a simple experiment that shows that pressure in liquids increases with depth.

5. A force of 5N is applied on a piston of area 0.05m2_{. This is connected using a hydraulic fluid}

with a second piston of area 0.2m2.

a. Why is a hydraulic fluid used instead of air? b. Why is a hydraulic fluid used instead of water? c. Calculate the pressure in the fluid.

d. Calculate the force exerted by the second piston.

6. A sample of gas is trapped in a syringe and heated. How will each of the following vary: a. Volume

b. Density

c. Pressure if the volume is kept constant

Work, Energy and Power

1. An object of mass 50kg is raised four storeys by a lifter. Each story is 3.5m high. a. What is the main energy transfer in the lifter if it runs on a fossil fuel? b. Calculate the work done by the lifter

c. Calculate the power output of the lifter if the object was lifted in 1 minute d. The lifter is rated at 200W.

i. Calculate its efficiency

ii. Why is the lifter not 100% efficient?

e. After having reached the maximum distance of four storeys, the object falls. i. What is the potential energy of the object at the top?

ii. What is the kinetic energy of the object just before it hits the ground? Give a reason for your answer.

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

8

Energy Sources

1. Define renewable and non-renewable sources of energy

2. Look at these sources of energy and answer the questions that follow: nuclear; fossil fuels; biomass; hydroelectric; solar; wind

a. Give three examples of fossil fuels

b. Classify the sources as renewable and non-renewable

c. Give two advantages and two disadvantages of each source of energy

Heat

1. Draw the arrangement of particles in a solid, liquid and a gas a. Use your diagrams to explain how solids expand

b. Use your diagrams to explain why conduction cannot occur in gases c. Use your diagrams to explain why convection cannot take place in solids d. How is heat transferred through a vacuum?

2. In an experiment, an 800g block of copper was heated using a heater of power 1kW for 10 seconds. The temperature rose by 31.25 K.

a. Calculate the specific heat capacity of copper.

b. Suggest two ways by which the experiment can be made more accurate

c. By looking at your answer in (a), suggest why copper is a good material for cooking utensils

d. Copper is not a good material to make handles of cooking utensils. Explain why and give a suitable material for such use.

3. Explain why solar panels a. Have a glass cover b. Are painted black

Earth and the Universe

1. Explain why:

a. The sun lies at the centre of the solar system, and not the Earth or any other planet b. We observe day and night on Earth

c. Mercury is hotter than Earth

d. The year on Jupiter is longer than that on Earth e. Pluto is not a planet

2. List some benefits of space exploration

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

9

Model Answers to Questions

Units and Measurements

1. The SI units used are: a. Metres, m b. Seconds, s

c. Kilogrammes per metre cubed, kg/m3 d. Kilogrammes, kg

2. Converted to SI units: a. 0.2 kg

b. 0.000025 m3 c. 8100 s d. 2,500 kg/m3 3. The apparatus used is

a. Measuring cylinder b. Metre rule

4. Two precautions taken are: a. For a measuring cylinder

i. Read readings from the bottom meniscus ii. Take readings at eye level

iii. Drop objects slowly b. For a metre rule

i. Avoid parallax errors by placing the eye vertically above the scale ii. Avoid end errors by starting from the zero mark

iii. Avoid large gaps between the object and the ruler

Density

1. An iron door has a volume of 2m x 1.2m x 5cm. a. The volume in m3 is: 2 x 1.2 x 0.05 = 0.12 m3

m = ρV = 0.12 x 7,870 = 944.4 kg b. Iron will:

i. Sink in water since iron’s density is more than that of water ii. Float on mercury since the density of iron is less than mercury’s.

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

10

Forces

1. Scalar quantities are ones that have size only, while vector measurements are those that have both size and direction.

2. An astronaut weighs 800 N on Earth. a. m = W/g = 800/10 = 80 kg on Earth b. 80 kg in outer space (mass is constant) c. 0 N in outer space (zero gravity) d. W = mg = 80 x 1.6 = 128 N 3. Labelled forces acting on a:

Hooke’s Law

1. Hooke’s law states that the extension of a spring is directly proportional to the force causing it given that the elastic limit is not exceeded.

2. From the graphs below

a. The first force-extension graph is of a material that obeys Hooke’s Law

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

11

Moments

1. Definitions

a. The centre of gravity of an object is the point from which all the weight of the object seems to act

b. A moment is the turning effect of a force, caused by a force acting at a distance from a pivot

2. A uniform metre rule is balanced from its 50cm mark on a pivot. A weight of 3.5N is placed on the 20cm mark while an object of unknown weight is placed on the 65cm mark when the ruler is in equilibrium.

a. The setup is shown below:

b. At equilibrium, the total clockwise moments equal the total anticlockwise moments. c. Fd = Fd

3.5 x 30 = x x 15 3.5 x 30 / 15 = 7 N

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

12

Pressure

1. Pressure is the force per unit area.

2. Stefan of mass 55kg sits on a chair of mass 5kg having four legs each of base area 0.04m x 0.04m.

a. W = mg = (55 + 5) x 10 = 600 N b. A = 0.04 x 0.04 x 4 (legs) = 0.0064 m2 c. P = F/A = 600 / 0.0064 = 93750 Pa

d. If he stands on two legs only, the pressure will double since the surface area will be halved. Pressure and area are inversely proportional.

3. Total pressure = pressure due to water + atmospheric pressure Total pressure = ρgh + 101,325 Pa

Total pressure = 1,150 x 10 x 16 + 101,325 Pa Total pressure = 285,325 Pa

4. A diagram to describe a simple experiment that shows that pressure in liquids increases with depth:

5. A force of 5N is applied on a piston of area 0.05m2. This is connected using a hydraulic fluid with a second piston of area 0.2m2.

a. Because air is compressible while liquids are not

b. A hydraulic fluid provides lubrication and protection against corrosion c. P = F/A = 5/0.05 = 100 Pa

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

13

a. Volume – increases b. Density – decreases

c. Pressure if the volume is kept constant - increases

Work, Energy and Power

1. An object of mass 50kg is raised four storeys by a lifter. Each story is 3.5m high. a. Chemical  Potential Energy / Work Done

b. Weight = mg = 50 * 10 = 500N (downward force) Distance = 3.5 * 4 = 14m

Work = Fs = 7000 J

c. P = E / t = 7000 / 60 = 116.7 W d. The lifter is rated at 200W.

i. % Efficiency = (Pout / Pin) * 100 = (116.7/200) * 100 = 58.3% ii. Energy is lost as heat and sound

e. After having reached the maximum distance of four storeys, the object falls. i. 7000 J

ii. 7000 J assuming that there are no energy losses (conservation of energy) iii. KE = ½ mv2

√ √

Energy Sources

1. A renewable source of energy is one that can be used over and over again. A non-renewable source of energy can be used only once.

2. Look at these sources of energy and answer the questions that follow: nuclear; fossil fuels; biomass; hydroelectric; solar; wind

a. Coal, oil and gas

b. Renewable: biomass; hydroelectric; solar; wind Non-renewable: nuclear; fossil fuels

c. Look at your notes for chapter 4 page 10 (or click here)

Heat

Physics Study Plan for Year 9 Final Examination

2012

GJ Zahra, B.Ed (Hons)

14

other apart and occupying more space

b. Conduction is the transfer of heat by particles touching each other. In gases particles can move about easily and rarely touch with other particles

c. Convection is the transfer of energy by movement of particles. Hot particles occupy more space due to expansion, become less dense and, as a result, rise upwards. In solids, particles are tightly held and cannot move about.

d. Since in a vacuum there are no particles, conduction and convection cannot take place. Heat in a vacuum can only be transferred by radiation.

2. In an experiment, an 800g block of copper was heated using a heater of power 1kW for 10 seconds. The temperature rose by 31.25 K.

a. H = Pt = 1000 * 10 = 10000J

b. The experiment can be made more accurate by i. Lagging the copper block

ii. Placing the block on an insulating base

c. Copper is a good material for cooking utensils because it has a low specific heat capacity.

d. Copper is not a good material to make handles of cooking utensils because it is a good conductor of heat. Wood/plastic are suitable materials for such use. 3. Explain why solar panels

a. Solar panels have a glass cover to trap heat inside

b. Solar panels are painted black because black is a good absorber of heat

Earth and the Universe

1. Explain why:

a. The sun lies at the centre of the solar system since it is the largest object in the solar system and, according to the law of gravity, it is light objects that orbit heavier ones b. The Earth spins on its own axis and takes 24 hours to do so. During day time, the

part of the Earth where we lie is facing the sun.

c. Mercury is hotter than Earth because it lies closer to the Sun which is the main source of energy in our solar system

d. Jupiter lies farther away than Earth from the Sun. As a result, the orbit of Jupiter is longer and it takes more time to orbit the sun

e. Pluto is not a planet because it has not cleared the path around its orbit 2. Benefits of space exploration include

a. Gain more knowledge about the place we live in b. Jobs for scientists

c. New technology

3. 8.6 years = 8.6 x 365 days x 24 hours x 60 minutes x 60 seconds = 2.71 x 108 s 1 s = 3 x 108 m