Motion · revision map · IGCSE 0625, Topic 1.2
TOPIC 1.2 · MOTION
CAMBRIDGE IGCSE PHYSICS 0625 · ONE-PAGE REVISION MAP
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MOTION1.2
Speed (scalar)
How fast something moves: distance per unit time.
v = s / ts = distance, t = time · unit m/s
- Scalar: size only, no direction.
Velocity (vector)
Speed in a stated direction. A vector: magnitude and direction.
Scalars
speed, distance, mass, time, energy
speed, distance, mass, time, energy
Vectors
velocity, displacement, force, acceleration
velocity, displacement, force, acceleration
Distance–Time Graphs
The gradient is the speed. A flat line means at rest; a steeper line means faster.
average speed = total distance ÷ total timeSpeed–Time Graphs
The gradient is the acceleration. A flat line means constant speed.
- Area under the line = distance travelled.
Acceleration
The rate of change of velocity, how much the velocity changes each second.
a = Δv / t
Δv = v − u
(change in velocity)
unit m/s²
(change in velocity)
unit m/s²
- Slowing down is a negative acceleration (deceleration).
Calculating from GraphsEXTENDED
- Acceleration = gradient of a speed–time graph (rise ÷ run).
- Distance = area under a speed–time graph.
- For a curve, draw a tangent to find the gradient.
Free Fall & Weight
In free fall, every object accelerates at g ≈ 9.8 m/s² (use 10 m/s²).
W = m gweight = mass × gravitational field strength
- Without air resistance, mass doesn't matter, all objects fall together.
- Weight always acts downward.
Terminal Velocity & FluidsEXTENDED
- Start: weight > drag, so it accelerates.
- Speeding up: drag grows, so acceleration falls.
- Terminal velocity: drag = weight, resultant force = 0, constant speed.
- Parachute opens: drag > weight, it decelerates to a new lower terminal velocity.