Physics: Motion, Forces, Energy, Electricity and Waves
What this domain covers
Grade 10 Physics focuses on describing motion, explaining forces, calculating energy transfers, understanding simple circuits, and using wave ideas including light. The exam rewards correct formulae, correct units and clear reasoning about cause and effect.
Core rules and concepts
- Speed = distance / time. Velocity is speed in a stated direction. Acceleration = change in velocity / time. Use consistent units, usually metres and seconds.
- Balanced forces produce no change in motion: an object stays at rest or moves at constant velocity. Unbalanced forces cause acceleration. Weight = mass x gravitational field strength, approximately 10 N/kg near Earth's surface.
- Work = force x distance moved in the direction of the force. Gravitational potential energy = mgh. Kinetic energy = 1/2 mv^2. Energy is conserved but can transfer to less useful forms such as heat.
- Ohm's law: V = IR. Electrical power: P = VI. In a series circuit, current is the same at all points; in parallel, branches share current and have the same voltage across them.
- Wave speed = frequency x wavelength. Reflection, refraction and absorption change the direction or intensity of light.
Worked example
A 5 kg box is lifted steadily through 2 m in 4 s. Take g = 10 N/kg. The weight is 5 x 10 = 50 N. The upward force needed is 50 N, so work done = 50 N x 2 m = 100 J. Power = work / time = 100 J / 4 s = 25 W. The reasoning is that a steady lift requires a force equal to the weight, and power measures energy transferred per second.
Traps that cost marks
Mass is not weight; mass is in kilograms and weight is a force in newtons. Distance is not displacement. In a series circuit, current is not used up by each bulb. Convert centimetres to metres and minutes to seconds before calculating. Do not write a speed as a velocity without a direction.