PHYSICS SUMMARY
GR 10-12
IEB
Rachel Jones and Shaida Jooma
,Physics Summary GR 10 – 12 IEB
General things to remember ......................................................................................................... 3
Mechanics ................................................................................................................................... 4
Resultant vectors ............................................................................................................................. 4
Equilibrium forces ............................................................................................................................ 6
Three ways to workout Normal Force ............................................................................................. 7
Drawing free body diagrams ............................................................................................................ 8
Coefficient of static friction.............................................................................................................. 9
Newton’s first law .......................................................................................................................... 10
Newton’s second law ..................................................................................................................... 11
Newton’s third law......................................................................................................................... 17
Explanation questions .................................................................................................................... 18
Momentum and Impulse ............................................................................................................... 19
Conservation of Momentum .......................................................................................................... 22
Work, Energy and Power ............................................................................................................ 24
Conservation of mechanical energy............................................................................................... 24
Work ............................................................................................................................................... 26
Work Energy Theorem ................................................................................................................... 27
Work done by non-conservative forces ......................................................................................... 28
Power ............................................................................................................................................. 29
The Photoelectric Effect .............................................................................................................. 30
Electroscope experiment: .............................................................................................................. 34
More on the photoelectric effect: ................................................................................................. 35
Conditions for the photoelectric effect ......................................................................................... 36
Analysis........................................................................................................................................... 36
Graphs ............................................................................................................................................ 37
Emission Spectrum ......................................................................................................................... 38
How increasing intensity of light affects current in a cell: ............................................................ 39
Electrodynamics ......................................................................................................................... 40
Electromagnet ................................................................................................................................ 41
The Motor Effect ............................................................................................................................ 43
DC Motor: (Direct Current Motor) ................................................................................................. 46
Lenz’s Law:...................................................................................................................................... 50
AC Generator: (Alternating Current Generator) ............................................................................ 51
Transformers .................................................................................................................................. 56
1|P age
R Jones and S Jooma
,Physics Summary GR 10 – 12 IEB
Gravitational Fields ............................................................................................................................ 59
Electric Fields and Electrostatic forces ............................................................................................... 64
Electrical circuits ........................................................................................................................ 71
Explanation questions: electric circuits ......................................................................................... 74
Ohmic Vs non-ohmic resistors ....................................................................................................... 76
Kinematics ................................................................................................................................. 77
Vertical projectile motion ........................................................................................................... 82
Mathematical relationships........................................................................................................ 87
2|P age
R Jones and S Jooma
,Physics Summary GR 10 – 12 IEB
General things to remember
• Always write down the formula.
• In physics mass should be in kilograms, unless otherwise stated.
• Make sure that you are using the proper measurement for the formula.
• Always put direction in your answer for vectors.
• Choose positive (+) and negative (-) directions when necessary.
• Remember to square numbers where there is a square in the formula.
Formulas:
• m = milli = 10-3
• μ= micro = 10-6
• n = nano = 10-9
• p = pico = 10-12
3|P age
R Jones and S Jooma
, Physics Summary GR 10 – 12 IEB
Mechanics
Scalar Quantities Vector Quantities
Distance Displacement
Doesn’t need direction. Mass Velocity Needs direction.
Area Acceleration
Work Force
Power Momentum
Resultant vectors
Example:
• 200 N North, 320 N East, find the resultant force.
Now complete the triangle by moving on of the
200 N lines that you have drawn.
North
320 N
East
I have moved the 200 N line to the left to
200 N compete the triangle, now I can use Pythagoras
North
to find the resultant force’s value.
320 N
East
FR 2 = 2002 + 3202
FR = 377.36 N
TAN = Opposite \ adjacent
TAN = 320/200 = 58
= 377,36 N 58 relative to the horizontal.
4|P age
R Jones and S Jooma
,Physics Summary GR 10 – 12 IEB
How to draw vectors
• Pull = up.
• Push = down.
Example:
• A man pulls a crate at an angle of 30 to the horizontal with a force of 250 N
• Workout the vertical component (fy) and the horizontal component (fx)
60 We can workout the other angle since a vector
Fy
like this will always have be a right-angled
30 triangle.
Fx
• Fy = F sin Do not forget to put direction.
• = 250 sin (60)
• Fy = 216,5 N right
• Fx = F cos.
• = 250 Cos 30
• Fx = 125 N up
Useful Formulae:
F (The horizontal force) = F cos
Fy (The vertical force) = F sin
Fg// (The force parallel to Gravity, AKA
mg(sin)
down the slope) =
Fg⊥ (The normal force on a slope) = mg(cos)
Note: you must know these formulae off by heart.
5|P age
R Jones and S Jooma
, Physics Summary GR 10 – 12 IEB
Equilibrium forces
• All the forces acting on the object is balanced out, therefore there is no resultant force.
• Therefore, we can further conclude that there is no acceleration and there is a constant
velocity.
Forces are in Equilibrium if:
1. FX1 = FX2
2. FY1 + FY2 = Fg
• If there is a mass on the pulley, make sure the mass is in Kilograms and then use the
formula Fg = mg to find the gravitational force.
• From there you can workout whether the forces are in equilibrium or not.
Example:
• Prove that these forces are not in equilibrium.
F = F cos
45 15
• F1 = 10 cos(15) = 9,66 N Right.
• F2 = 7 cos (45) = 4, 95 N Left.
F1 F2.
Fg = 2N
Fy = F sin
• Fy 1 = 10 sin (15) = 2,59 N Up
• Fy2 = 7 sin (45) = 4, 95 N Up
• Fg = 2N down.
Note
Fy1 + Fy2 Fg.
You have to draw in the blue and
green lines on the diagram to make
These forces are not in equilibrium.
a right-angled triangle, which will
help you solve F and Fy.
6|P age
R Jones and S Jooma
,Physics Summary GR 10 – 12 IEB
Three ways to workout Normal Force
1. When the applied force is at an angle (The object is flat on the surface)
2N
50
5 Kg
• Draw a free body diagram like the one on the right that shows FN , FY and Fg.
• Then make a formula using the free body diagram.
• Formula to use : Fn = Fg –Fy. FN Fy
• FN = [5 × 9.8] – [2 sin(50)]
• FN = 47,5 N Up.
Fg
2. Object on a slope
50
• Always use the formula for Fg⊥ (Because Fg⊥ is Normal force on a slope)
• Fg⊥ = mg cos .
• (5 × 9,8) cos (50)
• =31,5 N up.
3. Object is flat and there is no applied force at an angle.
5 Kg
• NF = mg
• = 5×9,8
• = 49 N up
7|P age
R Jones and S Jooma
, Physics Summary GR 10 – 12 IEB
Drawing free body diagrams
• Always write the force’s out in full, don’t abbreviate, unless you use a key.
Examples: Normal force
1. 60N
50
16N 5 Kg Frictional force
- - 50
-----
Gravitational force
2.
Frictional force
Normal force
50
50
Gravitational force
How to know where the angle goes:
• First decide where fg// and fg ⊥ are.
50
• Fg // is always down the slope.
• The angle will always be between fg anf fg ⊥. Fg//
Fg ⊥
• NB: you can only draw fg or its components (fg// and fg⊥) Fg
(Down the slope)
NOT both. The diagram on the right is just to show how
to find where to draw the angle.
Normal force
3.
50N
50
-- ---- -- ----
5 Kg 50 50 Frictional force
- -
Applied force
Gravitational force
8|P age
R Jones and S Jooma
GR 10-12
IEB
Rachel Jones and Shaida Jooma
,Physics Summary GR 10 – 12 IEB
General things to remember ......................................................................................................... 3
Mechanics ................................................................................................................................... 4
Resultant vectors ............................................................................................................................. 4
Equilibrium forces ............................................................................................................................ 6
Three ways to workout Normal Force ............................................................................................. 7
Drawing free body diagrams ............................................................................................................ 8
Coefficient of static friction.............................................................................................................. 9
Newton’s first law .......................................................................................................................... 10
Newton’s second law ..................................................................................................................... 11
Newton’s third law......................................................................................................................... 17
Explanation questions .................................................................................................................... 18
Momentum and Impulse ............................................................................................................... 19
Conservation of Momentum .......................................................................................................... 22
Work, Energy and Power ............................................................................................................ 24
Conservation of mechanical energy............................................................................................... 24
Work ............................................................................................................................................... 26
Work Energy Theorem ................................................................................................................... 27
Work done by non-conservative forces ......................................................................................... 28
Power ............................................................................................................................................. 29
The Photoelectric Effect .............................................................................................................. 30
Electroscope experiment: .............................................................................................................. 34
More on the photoelectric effect: ................................................................................................. 35
Conditions for the photoelectric effect ......................................................................................... 36
Analysis........................................................................................................................................... 36
Graphs ............................................................................................................................................ 37
Emission Spectrum ......................................................................................................................... 38
How increasing intensity of light affects current in a cell: ............................................................ 39
Electrodynamics ......................................................................................................................... 40
Electromagnet ................................................................................................................................ 41
The Motor Effect ............................................................................................................................ 43
DC Motor: (Direct Current Motor) ................................................................................................. 46
Lenz’s Law:...................................................................................................................................... 50
AC Generator: (Alternating Current Generator) ............................................................................ 51
Transformers .................................................................................................................................. 56
1|P age
R Jones and S Jooma
,Physics Summary GR 10 – 12 IEB
Gravitational Fields ............................................................................................................................ 59
Electric Fields and Electrostatic forces ............................................................................................... 64
Electrical circuits ........................................................................................................................ 71
Explanation questions: electric circuits ......................................................................................... 74
Ohmic Vs non-ohmic resistors ....................................................................................................... 76
Kinematics ................................................................................................................................. 77
Vertical projectile motion ........................................................................................................... 82
Mathematical relationships........................................................................................................ 87
2|P age
R Jones and S Jooma
,Physics Summary GR 10 – 12 IEB
General things to remember
• Always write down the formula.
• In physics mass should be in kilograms, unless otherwise stated.
• Make sure that you are using the proper measurement for the formula.
• Always put direction in your answer for vectors.
• Choose positive (+) and negative (-) directions when necessary.
• Remember to square numbers where there is a square in the formula.
Formulas:
• m = milli = 10-3
• μ= micro = 10-6
• n = nano = 10-9
• p = pico = 10-12
3|P age
R Jones and S Jooma
, Physics Summary GR 10 – 12 IEB
Mechanics
Scalar Quantities Vector Quantities
Distance Displacement
Doesn’t need direction. Mass Velocity Needs direction.
Area Acceleration
Work Force
Power Momentum
Resultant vectors
Example:
• 200 N North, 320 N East, find the resultant force.
Now complete the triangle by moving on of the
200 N lines that you have drawn.
North
320 N
East
I have moved the 200 N line to the left to
200 N compete the triangle, now I can use Pythagoras
North
to find the resultant force’s value.
320 N
East
FR 2 = 2002 + 3202
FR = 377.36 N
TAN = Opposite \ adjacent
TAN = 320/200 = 58
= 377,36 N 58 relative to the horizontal.
4|P age
R Jones and S Jooma
,Physics Summary GR 10 – 12 IEB
How to draw vectors
• Pull = up.
• Push = down.
Example:
• A man pulls a crate at an angle of 30 to the horizontal with a force of 250 N
• Workout the vertical component (fy) and the horizontal component (fx)
60 We can workout the other angle since a vector
Fy
like this will always have be a right-angled
30 triangle.
Fx
• Fy = F sin Do not forget to put direction.
• = 250 sin (60)
• Fy = 216,5 N right
• Fx = F cos.
• = 250 Cos 30
• Fx = 125 N up
Useful Formulae:
F (The horizontal force) = F cos
Fy (The vertical force) = F sin
Fg// (The force parallel to Gravity, AKA
mg(sin)
down the slope) =
Fg⊥ (The normal force on a slope) = mg(cos)
Note: you must know these formulae off by heart.
5|P age
R Jones and S Jooma
, Physics Summary GR 10 – 12 IEB
Equilibrium forces
• All the forces acting on the object is balanced out, therefore there is no resultant force.
• Therefore, we can further conclude that there is no acceleration and there is a constant
velocity.
Forces are in Equilibrium if:
1. FX1 = FX2
2. FY1 + FY2 = Fg
• If there is a mass on the pulley, make sure the mass is in Kilograms and then use the
formula Fg = mg to find the gravitational force.
• From there you can workout whether the forces are in equilibrium or not.
Example:
• Prove that these forces are not in equilibrium.
F = F cos
45 15
• F1 = 10 cos(15) = 9,66 N Right.
• F2 = 7 cos (45) = 4, 95 N Left.
F1 F2.
Fg = 2N
Fy = F sin
• Fy 1 = 10 sin (15) = 2,59 N Up
• Fy2 = 7 sin (45) = 4, 95 N Up
• Fg = 2N down.
Note
Fy1 + Fy2 Fg.
You have to draw in the blue and
green lines on the diagram to make
These forces are not in equilibrium.
a right-angled triangle, which will
help you solve F and Fy.
6|P age
R Jones and S Jooma
,Physics Summary GR 10 – 12 IEB
Three ways to workout Normal Force
1. When the applied force is at an angle (The object is flat on the surface)
2N
50
5 Kg
• Draw a free body diagram like the one on the right that shows FN , FY and Fg.
• Then make a formula using the free body diagram.
• Formula to use : Fn = Fg –Fy. FN Fy
• FN = [5 × 9.8] – [2 sin(50)]
• FN = 47,5 N Up.
Fg
2. Object on a slope
50
• Always use the formula for Fg⊥ (Because Fg⊥ is Normal force on a slope)
• Fg⊥ = mg cos .
• (5 × 9,8) cos (50)
• =31,5 N up.
3. Object is flat and there is no applied force at an angle.
5 Kg
• NF = mg
• = 5×9,8
• = 49 N up
7|P age
R Jones and S Jooma
, Physics Summary GR 10 – 12 IEB
Drawing free body diagrams
• Always write the force’s out in full, don’t abbreviate, unless you use a key.
Examples: Normal force
1. 60N
50
16N 5 Kg Frictional force
- - 50
-----
Gravitational force
2.
Frictional force
Normal force
50
50
Gravitational force
How to know where the angle goes:
• First decide where fg// and fg ⊥ are.
50
• Fg // is always down the slope.
• The angle will always be between fg anf fg ⊥. Fg//
Fg ⊥
• NB: you can only draw fg or its components (fg// and fg⊥) Fg
(Down the slope)
NOT both. The diagram on the right is just to show how
to find where to draw the angle.
Normal force
3.
50N
50
-- ---- -- ----
5 Kg 50 50 Frictional force
- -
Applied force
Gravitational force
8|P age
R Jones and S Jooma
