IGCSE 0625 · MECHANICS · 1.2

Motion

Speed, velocity, acceleration, and the graphs that tell the story of a journey, plus the Extended idea of free fall and terminal velocity. It builds on physical quantities and leads into forces and momentum.

TOPIC 1.2: MOTION CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 1.1 Quantities LEADS TO 1.5 Forces 1.6 Momentum MOTION & GRAPHS 1 · SPEED & VELOCITY Speed is how fast something moves. Velocity is speed in a stated direction. v = s / t s = distance t = time Speed is in metres per second (m/s). Average speed = total distance ÷ total time. 2 · ACCELERATION Acceleration is the change in velocity each second. a = Δv / t Δv = change in velocity Measured in metres per second squared (m/s²). Slowing down is a negative acceleration. 3 · MOTION GRAPHS Graphs tell the story of a journey. Distance-time: gradient is the speed; a flat line means at rest. Speed-time: gradient is the acceleration; the area underneath is the distance. s t distance-time v t speed-time 4 · FREE FALL & DRAG EXTENDED Near Earth, objects in free fall accelerate at g ≈ 9.8 m/s² (often taken as 10 m/s²). Air resistance grows as an object speeds up. When it balances the weight, the forces are balanced and the speed stays constant: this steady speed is the terminal velocity. speed time terminal velocity
TOPIC 1.2: MOTION CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 1.1 Quantities LEADS TO 1.5 Forces 1.6 Momentum MOTION & GRAPHS 1 · SPEED & VELOCITY Speed is how fast something moves. Velocity is speed in a stated direction. v = s / t s = distance t = time Speed is in metres per second (m/s). Average speed = total distance ÷ total time. 2 · ACCELERATION Acceleration is the change in velocity each second. a = Δv / t Δv = change in velocity Measured in metres per second squared (m/s²). Slowing down is a negative acceleration. 3 · MOTION GRAPHS Graphs tell the story of a journey. Distance-time: gradient is the speed; a flat line means at rest. Speed-time: gradient is the acceleration; the area underneath is the distance. s t distance-time v t speed-time 4 · FREE FALL & DRAG EXTENDED Near Earth, objects in free fall accelerate at g ≈ 9.8 m/s² (often taken as 10 m/s²). Air resistance grows as an object speeds up. When it balances the weight, the forces are balanced and the speed stays constant: this steady speed is the terminal velocity. speed time terminal velocity
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