Physics Exam Notes

Movement and Position

Average speed is calculated as: v = \frac{s}{t}
Units of speed include m/s and km/h.
To convert m/s to km/h, multiply by 3.6.
Distance can be calculated as: s = v \times t
Time can be calculated as: t = \frac{s}{v}
The slope of a distance-time graph indicates speed; a straight line signifies constant speed.
Displacement is distance in a specific direction; velocity is speed in a specific direction.
Average velocity is calculated as: average velocity = increase in displacement / time taken
Acceleration is the rate of change of velocity: a = \frac{v - u}{t}, where v is final velocity and u is initial velocity.
Acceleration is measured in m/s². Deceleration is negative acceleration.
The gradient of a velocity-time graph represents acceleration.
The area under a velocity-time graph represents the distance traveled.
Key equation: \v^2 = u^2 + 2as

Forces can change an object's speed, shape, or direction.
Examples of forces include gravitational, electrostatic, and magnetic forces.
Force is a vector quantity measured in Newtons (N).
Resultant force: the vector sum of all forces acting on an object. An unbalanced force causes acceleration.
Friction opposes motion.
Hooke’s Law: Within the elastic limit, the extension of a spring is proportional to the applied force.

Relationship between force, mass, and acceleration: F = m \times a
Weight is calculated as: W = m \times g, where g is gravitational field strength (approximately 9.8 N/kg on Earth).
Stopping distance = thinking distance + braking distance
Factors affecting stopping distance: speed, mass, road conditions, and reaction time.
Falling objects reach terminal velocity when air resistance equals weight.

Momentum is calculated as: p = m \times v
Force is related to change in momentum: F = \frac{mv - mu}{t}, where mv is final momentum and mu is initial momentum.
In collisions, neglecting external forces, total momentum is conserved.
Newton’s Third Law: For every action, there is an equal and opposite reaction.

Moment of a force = force × perpendicular distance from the pivot.
Weight acts through an object's centre of gravity.
The principle of moments: For an object in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments about a pivot.