Grade 9 Physics

By the end of this section you should be able to:

 Define the term vector. of vectors

• Give some examples of vector quantities.

• Represent vectors both analytically and graphically.

 • Define the term resultant vector.

• Add two vectors together (including vectors in the same direction, vectors opposite directions and at right angles to each other). Determine the angle of a resultant vector.

• Use Pythagoras’s theorem to determine the size of the resultant vector.

• Resolve a vector into horizontal and vertical components.

• Find the direction and resultant of two or more vectors using thecomponent method.

 • Define the term equilibrium.

 • Explain the importance of forming a triangle of three vectors.

• Carry out some experiments to investigate vectors.

• Describe the characteristics of uniform motion. • Define the terms distance, displacement, speed and velocity. • Explain the difference between distance and displacement. • Distinguish between average and instantaneous speeds and velocities. • Define the term acceleration. accelerated • Describe the meaning of the term uniformly accelerated motion. motion • Explain the meaning of the unit m/s2 • Use velocity–time graphs to determine the acceleration of an object. • Describe the key features of distance–time and displacement–time description of graphs. uniformly • Use displacement–time graphs to determine the velocity of an object. accelerated • Describe the key features of velocity–time graphs. motion • Use velocity–time graphs to determine the acceleration of an object and the displacement. • Describe the equations of uniformly accelerated motion. uniformly • Use these equations to solve problems. accelerated • Explain the importance of using the correct sign convention (+ or –) motion when dealing with velocities and accelerations. (page 28) • Define the meaning of the term free fall. • Apply the equations to solve problems relating to free fall. • Explain the meaning of the term reference point (or reference frame). velocity in one • Describe the relative velocities of objects. dimension • Calculate the relative velocity of a body with respect to another body when moving in the same or in the opposite direction.

• List some of the forces that occur in nature and categorise themas contact or non-contact.

• State Newton’s first law.

• Explain the relationship between mass and inertia.

• State Hooke’s law and distinguish between elastic and inelastic

materials.

• Experimentally determine and describe the force constant of a

spring.

• Distinguish between resultant force and equilibrant force.

• Describe the effect of a force acting on a body.

• Apply Newton’s second law (as Fnet = ma) to solve problems.

• Resolve forces into rectangular components and compose forces

acting on a body using component methods.

• Describe the terms weight and weightlessness (including

distinguishing between weight and apparent weight).

By the end of this section you should be able to:

•Calculate the weight and apparent weight of an object in a range

of situations.

• Explain the causes of frictional forces.

• Describe the differences between limiting friction, static friction

and kinetic friction.

• Draw free body diagrams for objects on inclined planes (to include

frictional forces) and use these diagrams to solve problems.

• State Newton’s third law.

• Describe experiments to demonstrate it and give examples of

where it is applicable.

• Define linear momentum and state its units.

• State the law of conservation of momentum.

• Define the term impulse and state its units.

• Solve numerical problems relating to momentum, conservation of

momentum and impulse.

• State Newton’s second law in terms of momentum.

• Distinguish between elastic and inelastic collisions

• State the conditions required for linear equilibrium.

• Decide whether a system is in equilibrium.

• Apply the first condition of equilibrium to solve problems.

By the end of this section you should be able to:

• Describe the necessary conditions for work to be done by a force

(including work done by a force F acting on a body at an angle of θ).

• Use W = F s cos θ to solve problems.

• Calculate the work done against gravity, the work done by a

frictional force and the work done by a variable force.

• Distinguish between negative and positive work.

• Explain the relationship between work and energy.

• Derive the relationship between work and kinetic energy and use

this to solve problems.

• Show the relationship between work and potential energy as

W = –ΔU and use this to solve problems.

• Describe gravitational potential energy and elastic potential

energy.

• Explain mechanical energy as the sum of kinetic and potential

energy.

• State the law of conservation of mechanical energy.

• Revise the term collision and distinguish between elastic and

inelastic collisions.

• Solve problems involving inelastic collisions in one dimension

using the laws of conservation of mechanical energy and

momentum.

• Explain the energy changes that take place in an oscillating

pendulum and an oscillating spring–mass system.

• Describe the use of energy resources, including wind energy, solar

energy and geothermal energy.

• Explain the meaning of the term renewable energy.

• Solve problems relating to the definition of power.

• Show that the kWh is also a unit of work.

• Express the formula of mechanical power in terms of average

velocity.

By the end of this section you should be able to:

• Explain the purposes of a machine.

• List the types of simple machines.

• Determine whether the machines are force multipliers, speed

multipliers or direction changers.

• Define the terms load, effort, work output, work input, mechanical

advantage (MA), velocity ratio (VR) and efficiency.

• Derive the expression of η = MA/VR from its definition.

• Derive an expression for MA of an inclined plane with or without

friction.

• Calculate MA, VR and efficiency of an inclined plane.

• Calculate MA, VR and efficiency of a wedge.

• Determine the MA, VR and efficiency of a lever.

• Identify the orders of a lever and give examples.

• Describe the use of a wheel and axle and determine MA, VR and

efficiency of a wheel and axle.

• Describe the use of gears.

• Describe different pulley systems and calculate MA, VR and

efficiency of a pulley system.

• Describe the use of a jackscrew

By the end of this section you should be able to:

• Define the term air pressure and use the definition to solve related

problems.

• Describe atmospheric pressure and explain its variation with

altitude.

• Explain how to measure atmospheric pressure and show that

760 mmHg is equal to one atmosphere.

• Define the term fluid and state the similarities and differences

between liquids and gases.

• Define the term density and relative density and determine each

for a given body.

• Explain how the pressure in a liquid at rest varies.

• Apply the formula p = hρg and use it to solve problems (including

determining the pressure inside a fluid taking into account

atmospheric pressure).

• State Pascal’s principle, and apply it to solve problems and explain

applications (such as the hydraulic lift).

• Explain the use of a manometer.

• Demonstrate an understanding of, distinguish between and

calculate atmospheric, gauge and absolute pressure.

• State Archimedes’s principle and the principle of flotation.

• Distinguish between true weight and apparent weight of a body.

• Calculate the buoyant force acting on the body in a fluid and

explain why bodies float or sink.

• Calculate the density of a floating body or density of a fluid using

the flotation principle.

By the end of this section you should be able to:

• Explain the difference between heat and temperature.

• Define the term thermal equilibrium.

• Describe the thermal expansion of solids and derive the expression

for the linear and surface expansion of solids.

• Find the relationship between the coefficient of linear, area and

volume expansion and solve related problems.

• Know applications of the thermal expansion of materials.

• Distinguish between apparent and real expansion of a liquid and

solve problems involving the expansion of liquids using V = Vo

γΔT.

• Explain the abnormal expansion of water.

• Compare the expansion of gases with the expansion of solids and

liquids.

• Describe the factors that affect the amount of heat absorbed or

liberated by a body.

• Define the terms specific heat capacity and heat capacity and

calculate the amount of heat energy absorbed or liberated by a

body using Q = mc∆T.

• Calculate the heat capacity of a body.

• Identify different units of heat energy.

• Explain the significance of the high specific heat capacity of

water.

• Use the relationship heat lost = heat gained to solve problems

involving heat exchange.

• Describe the uses of a calorimeter

• Define the terms latent heat, latent heat of fusion and latent heat

of vaporisation.

• Solve problems involving change of state.

By the end of this section you should be able to:

• Define the terms wave and wave pulse.

• Describe longitudinal and transverse waves.

• Define the terms compression and rarefaction.

• Define and identify the following features of a wave: crest, trough,

wavelength, frequency, amplitude and time period.

• Distinguish between mechanical waves and electromagnetic waves.

• Identify transverse and longitudinal waves in a mechanical media.

• State the wave equation and use it to solve problems.

• Describe the characteristic properties of waves, including

reflection, refraction, diffraction and interference.

• Define the terms diffraction and interference.

• Identify sound waves as longitudinal mechanical waves and

describe how they are produced and how they propagate.

• Compare the speed of sound in different materials and determine

the speed of sound in air at a given temperature.

• Define the intensity of a sound wave and solve problems using the

intensity formula.

• Explain the meaning of the terms echo, reverberation, pitch,

loudness and quality.

• Explain the reflection and refraction of sound and describe some

applications.