Section 1 General Physics

General Physics

PAL (IGCSE) Physics
Revision Book - Section 1

Name: _________________________________

Teacher: _________________________________ Syllabus Content_______________________________

Syllabus Details________________________________

1.1 Length and time
Core
• Use and describe the use of rules and measuring cylinders to calculate a length or a volume

THINGS TO REMEMBER...
Always align your eye with the position being measured
This avoids parallax errors

• Use and describe the use of clocks and devices for measuring an interval of time

THINGS TO REMEMBER...
Remember there is always a reaction time associated with using a clock or stopwatch

Supplement
• Use and describe the use of a mechanical method for the measurement of a small distance (including use of a micrometer screw gauge)

Micrometers are used to measure small distances accurately

• Measure and describe how to measure a short interval of time (including the period of a pendulum)

THINGS TO REMEMBER...
For measuring short intervals of time (when each period is the same), multiple measurements can be taken and then averaged

e.g. Period of a pendulum = Time for 10 oscillations / 10

1.2 Speed, velocity and acceleration
Core
• Define speed and calculate speed from total distance / total time

Symbol
Definition
SI unit
Vector / Scalar
Speed
v or u
Speed = total distance / total time m/s Scalar

• Plot and interpret a speed/time graph or a distance/time graph

• Recognise from the shape of a speed/time graph when a body is
– at rest
– moving with constant speed
– moving with changing speed

• Calculate the area under a speed/time graph to work out the distance travelled for motion with constant acceleration

• Demonstrate some understanding that acceleration is related to changing speed

Symbol
Definition
SI unit
Vector / Scalar
Acceleration
a
Acceleration
= change in velocity or speed / time m/s2 Vector (for changing v)

• State that the acceleration of free fall for a body near to the Earth is constant

Acceleration of free fall near the Earth is constant

All objects near the earth fall with a constant acceleration
The acceleration of free fall is NOT dependent on mass
The acceleration is ~10m/s2

Supplement
• Distinguish between speed and velocity

Symbol
Definition
SI unit
Vector / Scalar
Displacement
s
Distance moved in particular direction from a fixed point m Vector
Velocity
v or u
Velocity = change in displacement / time m/s Vector
Speed
v or u
Speed = total distance / total time m/s Scalar

Speed has magnitude but no direction - SCALAR Velocity has magnitude and direction - VECTOR

• Recognise linear motion for which the acceleration is constant and calculate the acceleration

Acceleration is constant if...

A constant resultant force acts
Eg.
Objects falling in a vacuum

Equations that can be used for constant acceleration...

v=u+at s=[(u+v)/2]/t v2=u2+2as s=ut+1/2at2 s=vt-1/2at2

• Recognise motion for which the acceleration is not constant

Acceleration is NOT constant if...

A varying resultant force acts
Eg.
Objects falling in air. The air resistance increases with velocity so the resultant force changes
A car accelerating. As the velocity of the car increases the air resistance also increases, so the resultant force changes.

• Describe qualitatively the motion of bodies falling in a uniform gravitational field with and without air resistance (including reference to terminal velocity)

1.3 Mass and weight
Core
• Show familiarity with the idea of the mass of a body
• State that weight is a force

• Demonstrate understanding that weights (and hence masses) may be compared using a balance

Supplement
• Demonstrate an understanding that mass is a property that ‘resists’ change in motion

• Describe, and use the concept of weight as the effect of a gravitational field on a mass

A gravitational field shows a region in which a mass will feel a force due to another mass nearby
The Earth is a very large mass so a strong gravitational field exists around it
Weight is the force acting on a mass due to the Earth’s gravitational field

1.4 Density
Core
• Describe an experiment to determine the density of a liquid and of a regularly shaped solid and make the necessary calculation

Supplement
• Describe the determination of the density of an irregularly shaped solid by the method of displacement, and make the necessary calculation

1.5 (a) Effects of forces
Core
• State that a force may produce a change in size and shape of a body

• Plot extension/load graphs and describe the associated experimental procedure

• Describe the ways in which a force may change the motion of a body

• Find the resultant of two or more forces acting along the same line

Supplement
• Interpret extension/load graphs

• State Hooke’s Law and recall and use the expression F = k x

• Recognise the significance of the term ‘limit of proportionality’ for an extension/load graph

• Recall and use the relation between force, mass and acceleration (including the direction)

REMEMBER:
Acceleration is a vector and so has direction
Force is a vector and so has direction

• Describe qualitatively motion in a curved path due to a perpendicular force
(F = mv2/r is not required)

1.5 (b) Turning effect
Core
• Describe the moment of a force as a measure of its turning effect and give everyday examples

• Describe qualitatively the balancing of a beam about a pivot
Supplement
• Perform and describe an experiment (involving vertical forces) to show that there is no net moment on a body in equilibrium
• Apply the idea of opposing moments to simple systems in equilibrium

1.5 (c) Conditions for equilibrium
Core
• State that, when there is no resultant force and no resultant turning effect, a system is in equilibrium

FOR A SYSTEM IN EQUILIBRIUM: There is no resultant force and no turning effect

1.5 (d) Centre of mass
Core
• Perform and describe an experiment to determine the position of the centre of mass of a plane lamina

Hang the lamina freely
Hang a plum line from the position the lamina is hang from
Draw a line along the plum line
Repeat this procedure for another position

• Describe qualitatively the effect of the position of the centre of mass on the stability of simple objects

1.5 (e) Scalars and vectors
Supplement
• Demonstrate an understanding of the difference between scalars and vectors and give common examples

SCALAR
VECTOR
Property with magnitude but no direction
Property with magnitude and direction
Example:
Speed
Distance
Pressure
Area
Volume
Work
Example:
Velocity
Acceleration
Force
Displacement

• Add vectors by graphical representation to determine a resultant
• Determine graphically the resultant of two Vectors

1.6 (a) Energy
Core
• Demonstrate an understanding that an object may have energy due to its motion or its position, and that energy may be transferred and stored

Energy... cannot be created or destroyed can be transferred from one form to another can be stored in to be transferred later

• Give examples of energy in different forms, including kinetic, gravitational, chemical, strain, nuclear, internal, electrical, light and sound

Energy Type
Example

Kinetic Energy
Moving objects (Car)
Gravitational Potential Energy
Raised objects (Water in a dam)
Chemical Energy
Energy stored in bonds (coal, oil)
Strain Energy
Energy due to flexing of materials (elastic band)
Nuclear Energy
Energy associated with atomic nuclei (Fission reactors)
Internal Energy
Energy of materials – kinetic from particles moving + potential from bonds
Electrical Energy
Energy from moving charges (electricity)
Light Energy
Energy from Electromagnetic waves (light, IR)
Sound Energy
Energy due to vibrating particles (sound)

• Give examples of the conversion of energy from one form to another, and of its transfer from one place to another

• Apply the principle of energy conservation to simple examples

For any change to occur in nature energy must be transferred.
Energy is not created or destroyed it is changed from one form into another

Supplement
• Recall and use the expressions k.e. = ½ mv 2 and p.e. = mgh

1.6 (b) Energy resources
Core
• Distinguish between renewable and non-renewable sources of energy

Non-renewable: Energy sources that when used cannot be replaced (or at least it will take millions of years).e.g. Coal, Oil Natural gas.
Renewable: Energy sources which can be used repeatedly without being used up. Solar energy, Wind, Tidal etc.
• Describe how electricity or other useful forms of energy may be obtained from:
– chemical energy stored in fuel

Coal can be burnt to release thermal energy - which heats water and makes it move – which turns a generator – which generates electricity

– water, including the energy stored in waves, in tides, and in water behind hydroelectric dams
Water stored behind a dam or tidal barrier can be allowed to flow down – this moving water turns a generator – which generates electricity – geothermal resources

Cold water is pumped underground – the earth warms the water which rises – this moving water turns a generator – which generates electricity

– nuclear fission

Atoms are split in a nuclear reactor – this releases energy which heats water – the water moves and turns a generator – which generates electricity

– heat and light from the Sun (solar cells and panels)

Solar energy from the sun can be converted directly into electricity using a solar cell
Solar energy can also be used to heat water directly (IR)

• Give advantages and disadvantages of each method in terms of cost, reliability, scale and environmental impact

Energy Source
Cost
Reliability
Scale
Environmental Impact
Chemical (Coal)
Low
Reliable
Large
High
Hydroelectric / tidal
High initially
Reliable (unless a drought)
Large
High
Geothermal
High initially
Reliable
Small
Low
Nuclear
High
Reliable
Large
Low
Solar Energy
High
Unreliable (only available during the day)
Small
Low

• Show a qualitative understanding of efficiency

In any energy transfer process energy is “lost” to non-useful forms.

CAR: Chemical Energy is converted to kinetic energy (useful) + Thermal energy (waste)

Supplement
• Show an understanding that energy is released by nuclear fusion in the Sun

NUCLEAR FUSION IN THE SUN

In the Sun hydrogen nuclei fuse together to form helium nuclei
In this process energy is released

• Recall and use the equation: efficiency = useful energy output / energy input × 100%

Efficiency = useful output energy / useful input energy

Percentage Efficiency = ( useful output energy / useful input energy ) x 100

In the transfer of energy from one form into another, there will always be losses, normally to heat energy.

The efficiency of the process tells use how much useful energy we get and how much is lost

1.6 (c) Work
Core
• Relate (without calculation) work done to the magnitude of a force and the distance moved
Supplement
• Describe energy changes in terms of work done
• Recall and use ΔW = Fd = ΔE

EXAMPLES OF WORK BEING DONE

A car engine does work against friction and accelerating the car
When you lift an object you do work against gravity

1.6 (d) Power
Core
• Relate (without calculation) power to work done and time taken, using appropriate examples
Supplement
• Recall and use the equation P = E/t in simple Systems

1.7 Pressure
Core
• Relate (without calculation) pressure to force and area, using appropriate examples

• Describe the simple mercury barometer and its use in measuring atmospheric pressure

The height of the mercury column relates to the atmospheric pressure

• Relate (without calculation) the pressure beneath a liquid surface to depth and to density, using appropriate examples

• Use and describe the use of a manometer

• Recall and use the equation p = F/A

• Recall and use the equation p = hρg