Physics Exam study guide

1. Scalars and Vectors

Scalar Quantities

Have magnitude only.

Examples:

• Distance

• Speed

• Mass

• Time

• Temperature

• Energy

Vector Quantities

Have magnitude and direction.

Examples:

• Displacement

• Velocity

• Acceleration

• Force

• Momentum

• Weight

Vector Addition

• Same direction → Add.

• Opposite direction → Subtract.

• Direction of larger vector is the answer.

Example:

5 N East + 3 N East

= 8 N East

2. Newton’s Laws of Motion

First Law (Law of Inertia)

An object remains at rest or moves with constant velocity unless acted upon by an unbalanced force.

Examples:

• Seat belts in cars.

• A book remains on a table until pushed.

Second Law

Force = Mass × Acceleration

Formula

F = ma

Units:

• Force = Newton (N)

• Mass = kg

• Acceleration = m/s²

Example:

Mass = 4 kg

Acceleration = 3 m/s²

Force = 4 × 3

= 12 N

Third Law

For every action, there is an equal and opposite reaction.

Examples:

• Rocket propulsion.

• Gun recoil.

• Walking.

3. Momentum

Momentum = Mass × Velocity

Formula

p = mv

Unit:

kg m/s

Example:

Mass = 5 kg

Velocity = 4 m/s

Momentum = 20 kg m/s

Conservation of Momentum

Total momentum before collision = Total momentum after collision

4. Energy

Kinetic Energy

Energy due to motion.

Formula:

KE=\frac12mv^2

Unit:

Joule (J)

Example:

m = 2 kg

v = 5 m/s

KE = ½ × 2 × 25

= 25 J

Potential Energy

Energy due to position.

Formula:

PE = mgh

Where:

• m = mass

• g = 10 m/s²

• h = height

Example:

2 kg object at height 5 m

PE = 2 × 10 × 5

= 100 J

Law of Conservation of Energy

Energy cannot be created or destroyed, only converted from one form to another.

Forms of Energy

• Heat

• Light

• Electrical

• Sound

• Chemical

• Nuclear

• Kinetic

• Potential

Renewable Energy Sources

5. Gas Laws

Boyle’s Law

At constant temperature:

Pressure is inversely proportional to volume.

P_1V_1=P_2V_2

If volume decreases, pressure increases.

Charles’ Law

At constant pressure:

Volume is directly proportional to temperature.

\frac{V_1}{T_1}=\frac{V_2}{T_2}

Temperature must be in Kelvin.

K = °C + 273

Pressure Law

At constant volume:

\frac{P_1}{T_1}=\frac{P_2}{T_2}

6. Thermal Expansion

Solids

Linear Expansion

Increase in length when heated.

Applications:

• Expansion gaps in bridges.

• Railway tracks.

Liquids

Expand more than solids.

Example:
Mercury in thermometers.

Gases

Expand the most.

Applications:

• Hot air balloons.

7. Pressure

Formula

Pressure=\frac{Force}{Area}

P=\frac{F}{A}

Unit:

Pascal (Pa)

1 Pa = 1 N/m²

Liquid Pressure

P=\rho gh

Pressure increases with:

• Depth.

• Density.

• Gravity.

Atmospheric Pressure

Measured using:

• Barometer

Uses:

• Weather forecasting.

PAPER 2 – STRUCTURED QUESTIONS

8. Graphs

Distance-Time Graph

Slope = Speed

Horizontal line = Object at rest

Steeper slope = Faster speed

Velocity-Time Graph

Slope = Acceleration

Area under graph = Distance travelled

Positive slope = Acceleration

Negative slope = Deceleration

Horizontal line = Constant velocity

9. Velocity and Acceleration

Speed

Speed=\frac{Distance}{Time}

Unit:

m/s

Velocity

Velocity = Displacement ÷ Time

(Direction included)

Acceleration

Acceleration=\frac{Final\ velocity-Initial\ velocity}{Time}

a=\frac{v-u}{t}

Unit:

m/s²

SUVAT Equations

1. 1.

v=u+at

2. 2.

s=ut+\frac12at^2

3. 3.

v^2=u^2+2as

Where:

• u = initial velocity

• v = final velocity

• a = acceleration

• s = displacement

• t = time

10. Simple Pendulum (Lab 6)

Apparatus

• Retort stand

• String

• Bob

• Stopwatch

• Metre rule

Procedure

1. Measure length of string.

2. Pull bob slightly aside.

3. Release without pushing.

4. Measure time for 20 oscillations.

5. Divide by 20 to find period.

Formula

T=\frac{time}{number\ of\ oscillations}

Where:

T = period (s)

Variables

Independent Variable:

• Length of string.

Dependent Variable:

• Period of oscillation.

Controlled Variables:

• Mass of bob.

• Amplitude.

Conclusion

As the length increases, the period increases.

CXC Formulas to Memorize