Grade 9 Semester Exam – PhysicsYou will be given an exam with all the questions from previous iGCSE exam papers. It will last 1 hourThe exam will be approximately split into 3 sections:

A. 30% Multiple ChoiceB. 50% Extended answer questions,C. 20% Practical questions

1. MotionDistance, Speed/Velocity, Acceleration, Motion graphs. Understand what the slope of the graphs mean. Make sure you remember that the area under a v-t graph is the distance travelled. This is commonly asked on exams. Learn the equations!! speed=distance/time, acceleration=Change in Speed/time

2. Forces & MotionF=ma, Resultant forces, Parachutists falling, cars moving forward. Learn how to cancel out the forces

3. PressureP=F/A, Why are ski's wide? Knives sharp?

4. MaterialsBasic stuff like – compression squashes bonds between atoms, tension stretches bonds, when things are bent there are compression forces on the shorter side and tension forces on the stretched side.

5. SpringsHooke's Law, Force-Extension graphs, Force-Length graphs, Elastic limit.

6. Changes of StateYou need to know that when things melt or boil the temperature doesn't change. Recognise the graph!! Energy is being used to break the bonds so it can't be used to raise the temperature (increase particle KE)

7. Kinetic TheoryHeating an object increases the kinetic energy of the particles. At Absolute zero particles have stopped. Convert °C into K (+273). Apply this knowledge. Explain the following using Kinetic Theory: (use: Particle/Kinetic Energy/Collisions/Force)

Expansion of solids (eg. railway tracks, thermometers, bridges) Evaporation of liquids If T ↑ then V↑ If T ↑ then P ↑ If V↓ then P ↑

8. Gas LawsLearn the gas law and make sure you can apply it in calculations. Always use Kelvins for temperature. Don't forget!

9. Heat Transfer Conduction - solids, metals (because of their free electrons), particles vibrating. Air is a brilliant insulator

because the particles are far apart, a vacuum is the best Convection - liquids, warm means less dense, cold means more dense, convection currents move the heat,

the wind is caused by them, sea breezes, Why are heaters low down? Air con high up? Radiation – infra-red, heat as waves, only one that doesn't need particles, black/dull – good absorber and

emitter, Shiny white or silver - good reflector and bad emitter. Evaporation – transfers heat by the hottest liquid particles escaping as a gas, leaves colder liquid behind

10. Difference between heat and temperatureWhy can you catch a 10,000K spark, but a hot bath at 50°C could burn you?

11. Heat CapacityAn object with a high heat capacity stores a lot of heat without the temperature rising much

12. Specific Heat CapacityHeat = m * c * ∆T – this is the heat needed to raise 1 Kg of a material by 1 °C (or K)Learn how to use the equation. What is unusual about water?

13. Energy Resources Non-Renewable – Fossil Fuels, Nuclear Renewable – Wind, Solar, Wave, Tidal, Geothermal, Hydro-Electric, Biomass

Learn how they work and the advantages and disadvantages of each method.14. Types of Energy & Energy Conservation

Sound, Light, Heat (Thermal), Electrical, Kinetic, Chemical Potential, Gravitational Potential, Strain/Elastic Potential.Energy cannot be created or destroyed, just changed from one type into another.

15. EfficiencyEverything wastes heat, so nothing is 100% efficient. Most machines are about 35% efficient, they waste lots of heat energy (and sometimes a bit of sound). Efficiency = output/input. It can be a number like 0.5 or we can write 50%. They mean the same thing. Old lightbulbs are about 2% efficient.

16. Kinetic Energy & Potential EnergyFalling objects turn their Potential Energy into Kinetic Energy as they fall. The KE just before they hit the ground = the PE at the top. KE=½mv². PE = mgh or Weight x height

17. Work & PowerDoing Work means using energy to move something. Work is measured in Joules.Work = Force x distance & Power = Work/Time.

18. DensityDensity = mass / volume. Learn how to find the density of an irregular and regular shaped object.

EquationsLearn them and write them in words if you are unsure about the correct symbols. Remember the units too!

Speed = Distance÷Time Acceleration = Change in Speed÷Time Taken

Force = Mass x Acceleration F=ma Pressure = Force ÷ Area Density = Mass ÷ Volume

Work = Force x (distance moved in direction of force) Wk=FsPower = Work ÷ Time or

Weight = mass x gravity Wt=mg (g=10N/Kg)

K.E.=½mv² P.E.=Wth Efficiency = Useful Output÷Total Input

Heat = mass x specific heat capacity x temperature change Q = mcΔT

Gas Law Remember that the Temperature should be in Kelvins (+273)(This equation nearly always has one variable that cancels out)

Unitsmass, Kg Force, N Weight, N Time, sHeat, J, kJ Specific Heat Capacity J/Kg°C Temperature, °C or KVolume, cm³, m³ Density, Kg/m³ Pressure, N/m², Pascals, Atmospheres, Bar, mbardistance, m velocity, m/s acceleration, m/s²Work, J Power, W efficiency, none or %