physics

What is a force?

A push, pull, or twist that can change an object’s motion, shape, or direction. Example: Gravity pulls an apple down.

What are the units of force?

Newtons (N). Example: 1\ N = \text{force needed to accelerate}\ 1\ kg\ \text{by}\ 1\ m/s^2.

What tool measures force?

A spring balance or force meter.

What is weight?

The force of gravity on an object. Example: Weight = mass × gravity (W = m \times g).

What is the difference between mass and weight?

Mass = amount of matter (kg), constant; weight = gravitational force (N), changes with gravity.

What is gravity on Earth?

9.8\ m/s^2 (≈ 10\ m/s^2).

What is friction?

A force that opposes motion between two surfaces. Example: Tyres on road.

What reduces friction?

Lubrication, smooth surfaces, wheels.

What is air resistance (drag)?

Friction caused by air particles opposing motion. Example: Parachute slows fall.

What is tension?

Force through a stretched string or rope.

What is normal force?

The upward force from a surface supporting an object’s weight.

What is net force (resultant force)?

Total force acting after combining all individual forces. Example: 10\ N right – 4\ N left = 6\ N right.

What happens if net force = 0\ N?

Object stays still or moves at constant speed.

What happens if net force \neq 0\ N?

Object accelerates in direction of the larger force.

What is Newton’s First Law?

An object stays at rest or moves at constant speed unless acted on by an unbalanced force.

What is Newton’s Second Law?

Force = mass × acceleration (F = m \times a). Example: 2\ kg \times 3\ m/s^2 = 6\ N.

What is Newton’s Third Law?

Every action has an equal and opposite reaction. Example: Rocket pushes gases down → gases push rocket up.

What is acceleration?

Rate of change of velocity. Equation: a = (v – u)/t.

What are the units of acceleration?

m/s^2.

What is speed?

Distance ÷ time. Example: 100\ m in 10\ s = 10\ m/s.

What is velocity?

Speed in a given direction. Example: 10\ m/s north.

What is the unit of distance?

Metres (m).

What is a distance–time graph?

A graph showing how distance changes over time. Example: Steeper slope = faster speed.

What is a velocity–time graph?

Shows how velocity changes over time. Example: Area under graph = distance travelled.

What is work?

Energy transferred when a force moves an object. Equation: W = F \times d.

What are the units of work?

Joules (J).

What is power?

Rate of doing work. Equation: P = W / t.

What is kinetic energy?

Energy of motion. Equation: \frac{1}{2}mv^2.

What is potential energy?

Stored energy due to position or height. Equation: E_p = mgh.

What is energy measured in?

Joules (J).

What is the law of conservation of energy?

Energy cannot be created or destroyed, only changed form.

What is efficiency?

Useful energy output ÷ total energy input × 100%.

What is current?

Flow of electric charge per second. Unit: Amperes (A).

What is voltage (potential difference)?

Energy given to charges per coulomb. Unit: Volts (V).

What is resistance?

Opposition to current flow. Unit: Ohms (\Omega). Equation: R = V / I.

What is Ohm’s Law?

Current is directly proportional to voltage if resistance is constant. Equation: V = I \times R.

What is a series circuit?

Components connected one after another. Example: One path for current.

What is a parallel circuit?

Components connected across multiple branches. Example: Each branch gets full voltage.

How does current behave in series?

Same through all components.

How does current behave in parallel?

Splits across branches.

How does voltage behave in series?

Shared between components.

How does voltage behave in parallel?

Same across each branch.

What device measures current?

Ammeter, connected in series.

What device measures voltage?

Voltmeter, connected in parallel.

What is electrical power?

Rate of energy transfer. Equation: P = V \times I.

What is the unit of energy in electricity?

Joule (J) or kilowatt-hour (kWh).

What safety devices prevent overload?

Fuses, circuit breakers.

What are conductors and insulators?

Conductors let current flow (metals), insulators don’t (plastic).

What is static electricity?

Build-up of electric charge on a surface.