GRADE 11 PHYSICS Chapter 1 (revision notes)

Scalars & Vectors

• Scalars have only magnitude (e.g., mass, distance).

• Vectors have both magnitude and direction (e.g., velocity, displacement).

• Magnitude is size.

Speed & Velocity

• Speed: Distance covered per unit of time (scalar).

• Velocity: Speed with a direction (vector). The relationship is given by:

  [ v = \frac{d}{t} ]

Where, ( v ) is velocity, ( d ) is distance, and ( t ) is time.

Average Speed

• Calculated if speed is not constant: ( \text{Average Speed} = \frac{\text{Distance}}{\text{Time}} )

Acceleration

• Defined as the change in velocity over time: ( a = \frac{\Delta v}{\Delta t} )

Distance-Time Graphs

• Shows how distance changes over time; slope indicates speed.

1.3 Mass, Weight & Density

Mass

• The quantity of matter in an object (scalar). Unit: kg.

Weight

• Gravitational force on mass, vector. ( W = m \times g ) (g = 9.81 N/kg).

Density

• Mass per unit volume. ( \rho = \frac{m}{V} )

1.4 Forces and Motion

Force

• A push or pull affecting an object's motion.

Resultant Forces

• Combination of all forces acting on an object.

1.5 Moments

Moment of a Force

• ( M = F \times d )

• Depends on force and perpendicular distance from pivot.

Principle of Moments

• In equilibrium, total clockwise moment = total anticlockwise moment.

1.6 Energy, Work & Power

Energy Transfer

• Energy transferred via different pathways: mechanical, electrical, heating, and radiation.

Work Done

• Work = Force × Distance (Joules).

Power

• Rate of energy transfer: ( P = \frac{W}{t} )

Efficiency

• Ratio of useful energy output to total energy input (%)

1.7 Energy from Various Sources

Solar Energy

• Renewable and harnessed via solar cells for electricity production.

Fossil Fuels

• Non-renewable, coal, oil, and gas - significant current dependency.

Biomass and Biofuels

• Renewable but takes land and resources.

Nuclear Energy

• Generated through fission, non-renewable but relatively low pollution.

Geothermal Energy

• Sustainable but location-dependent.

1.8 Pressure

Definition

• Pressure = Force/Area (Pascals).

Fluid Pressure

• In liquids/gases, increases with depth and density.

Summary of Formulas

1.2 Motion

• Speed: ( v = \frac{d}{t} ) (speed is distance over time).

• Average Speed: ( \text{Average Speed} = \frac{\text{Distance}}{\text{Time}} )

• Acceleration: ( a = \frac{\Delta v}{\Delta t} ) (change in velocity over time).

1.3 Mass, Weight & Density

• Weight: ( W = m \times g ) (gravitational force on mass).

• Density: ( \rho = \frac{m}{V} ) (mass per unit volume).

1.4 Forces and Motion

• Moment of a Force: ( M = F \times d ) (force times perpendicular distance).

• Principle of Moments: Total clockwise moment = total anticlockwise moment.

1.6 Energy, Work & Power

• Work Done: ( \text{Work} = \text{Force} \times \text{Distance} ) (in Joules).

• Power: ( P = \frac{W}{t} ) (rate of energy transfer).

• Efficiency: Ratio of useful energy output to total energy input (%).

1.8 Pressure

• Pressure: ( P = \frac{F}{A} ) (force per area).