Mechanics and WEP summary GR 10 – 12 IEB
Contents
Mechanics ............................................................................................................................................ 2
Resultant vectors................................................................................................................................ 2
Equilibrium forces .............................................................................................................................. 4
Three ways to workout Normal Force ............................................................................................... 5
Drawing free body diagrams .............................................................................................................. 6
Coefficient of static friction ............................................................................................................... 7
Newton’s first law .............................................................................................................................. 8
Newton’s second law ......................................................................................................................... 9
Newton’s third law ........................................................................................................................... 15
Explanation questions ...................................................................................................................... 16
Momentum and Impulse ................................................................................................................. 17
Conservation of Momentum ............................................................................................................ 20
Work, Energy and Power ................................................................................................................ 22
Conservation of mechanical energy ................................................................................................ 22
Work ................................................................................................................................................. 24
Work Energy Theorem ..................................................................................................................... 25
Work done by non-conservative forces........................................................................................... 26
Power ................................................................................................................................................ 27
1|Page
, Mechanics and WEP 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 one of
200 N the 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.
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, Mechanics and WEP 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) = mg(cos)
Note: you have to know these formulae off by heart.
3|Page
Contents
Mechanics ............................................................................................................................................ 2
Resultant vectors................................................................................................................................ 2
Equilibrium forces .............................................................................................................................. 4
Three ways to workout Normal Force ............................................................................................... 5
Drawing free body diagrams .............................................................................................................. 6
Coefficient of static friction ............................................................................................................... 7
Newton’s first law .............................................................................................................................. 8
Newton’s second law ......................................................................................................................... 9
Newton’s third law ........................................................................................................................... 15
Explanation questions ...................................................................................................................... 16
Momentum and Impulse ................................................................................................................. 17
Conservation of Momentum ............................................................................................................ 20
Work, Energy and Power ................................................................................................................ 22
Conservation of mechanical energy ................................................................................................ 22
Work ................................................................................................................................................. 24
Work Energy Theorem ..................................................................................................................... 25
Work done by non-conservative forces........................................................................................... 26
Power ................................................................................................................................................ 27
1|Page
, Mechanics and WEP 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 one of
200 N the 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.
2|Page
, Mechanics and WEP 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) = mg(cos)
Note: you have to know these formulae off by heart.
3|Page
