Term 2 Physics - Motion

What are significant figures?

Digits in a number that show its precision

What are significant figurs?

More significant figures = more precise measurement

Rules for identifying significant figures

All non-zero digits are significant

A rule for identifying significant figures

Zeros between non-zero digits are significant

Rules for identifying significant figures

Leading zeros (e.g. 0.05) are not significant

Trailing zeros

Without decimal is not significant (e.g. 129000)

Trailing zeros

With decimals is significant (e.g. 50.0)

A rule for identifying signifcant figures

Scientific notation: all digits in coefficient are significant

Addition and Subtraction

Round to the least number of decimal places

An example of Addition and Subtraction

5.0 + 0.08 = 5.08 → 5.1

Multiplication & Division

Round to the least number of significant figures

Example of multiplication and Division

5 × 13 = 65 → 70 (1 s.f.)

Key rule of Significant Figures

Final answer cannot be more precise than the least precise value used

Scalar

Magnitude only (e.g. 5kg, 60km/h)

Vector

Magnitude + direction (5 m north, 60 km/h east)

Distance

Is the total path travelled (scalar)

Displacement

Is the change in position + direction (vector)

Speed

Is how fast (scalar)

Velocity

Is the speed + direction (vector)

Acceleration

Is rate of change of velocity

Acceleration

Is a vector quantity

Acceleration Unit is

m/s²

Vectors must include:

Magnitude, unit and direction

Drawn as arrows

Length = magnitude and arrow tip = direction

Vector Addition (1D)

• Same direction → add

Vector Addition (1D)

• Opposite direction → subtract

Example of Vector Addition:

5 m right + 15 m right = 20 m right

Example of Vector Addition:

• 4 m/s north + 7 m/s south = 3 m/s south

Distance (s)

Is how far (unit: m)

Time (t)

Is how long (unit: s)

Speed (v)

Is the rate of motion (m/s)

Non-accelerated motion

Objects moves with constant velocity

Non-accelerated motion

Means constant speed and direction

Speed Formula

v=Δs/Δt

Distance formula

• Δs=v×t

Time formula

• Δt=s/v

1km in m

Is 1000 m

1cm in m

Is 0.01 m

1mm in m

Is 0.001 m

1 min in seconds

Is 60 s

1 h in seconds

Is 3600 s

Speed conversions

• km/h → m/s: ÷ 3.6

Speed Conversions

• m/s → km/h: × 3.6

Important tip

Always make sure units match before calculating

Significant Figures

Is accuracy and precision rules

Scalars / Vectors

Is whether direction matters

Motion

Is formulas + units + constant velocity

What is accelerated motion?

Motion where velocity changes over time

Accelerated motion can be:

Speeding up, Slowing down, Changing direction

What is acceleration?

Rate of change of velocity

Acceleration formula is

a=(v−u)/t

Acceleration unit is

m/s²

Is Acceleration scalar or vector

Acceleration is a vector (has direction)

Important ideas of acceleration is

Positive/negative values show direction, not just speeding/slowing

Important Idea of acceleration

Constant acceleration is assumed in this topic

Average velocity is

total displacement ÷ total time

Instantaneous velocity is

velocity at a specific moment

If they have no acceleration

They are the same

First SUVAT Equation is

v = u + at

Second SUVAT Equation is

s = ut + ½ at²

Third SUVAT equation is

v² = u² + 2as

What does u mean in SUVAT

u = initial velocity

What does V mean in SUVAT

v = final velocity

What does a mean in SUVAT

a = acceleration

What does t mean in SUVAT

t = time

What does s mean in SUVAT

s = displacement

Problem-solving tips

Gravity basics are

All objects with mass attract each other

Gravity basics are

Earth pulls objects downward

Gravity basics are

This causes acceleration

What does gravity (g) equal

g= 9.8 m/s²

Acceleration due to gravity is

Always acts downwards

Acceleration due to gravit is a

Constant (if air resistance is ignored)

Key idea of Accleration due to gravity

Objects speed up by 9.8 m/s every second as they fall

Effect of mass is

With no air resistance, all objects fall at the same rate

Effect of mass is

Mass does not affect fall speed

Dropping objects: inital velocity is

u = 0

Formulas of dropping objects is

v = gt

Formulas for dropping objects

s = ½ gt²

Throwing objects downwards

Initial velocity is not zero

Throwing objects downwards

Use full SUVAT equations

Throwing objects downwards

All motion is in same direction (down)

Throwing objects upwards

Upwards motion: slows down due to gravity

Throwing objects upwards: it’s highest point

v=0

Throwing objects upwards

• Then falls back down (accelerates downward)

Direction convention

Choose a direction as positive: up = positive (common) and down = negative

Direction convention key

Be consistent

Accelerated Motion

Velocity changes

Accelerated Motion

Use SUVAT equations

Acceleration can be

+ or −

Gravity equals

• g=9.8 m/s² downward

Gravity is

All objects fall at same rate (no air resistance)

Gravity is

Special case of accelerated motion

Graphs: Qualitative Description (no numbers)

Step 1: Look at how the y-value changes as x increases

What do you write for qualitive description for graphs

As the independent variable increased, the dependent variable increased / decreased / stayed constant

Step 2: Rate of change (gradient)- check if gradient

What do you write for rate of change (gradient)

… at a constant / decreasing / increasing rate.

What do you write for increasing constant

→ … increased at a constant rate

What do you write for increasing slowing down

→ … increased at a decreasing rate