Momentum · revision map · IGCSE 0625, Topic 1.6
TOPIC 1.6 · MOMENTUM
CAMBRIDGE IGCSE PHYSICS 0625 · ONE-PAGE REVISION MAP
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MOMENTUM1.6
MomentumEXTENDED
Momentum measures how hard it is to stop a moving object.
p = m v
p = momentum (kg m/s)
m = mass (kg)
v = velocity (m/s)
m = mass (kg)
v = velocity (m/s)
- A vector: direction matters.
- More mass or more speed means more momentum.
Force & ImpulseEXTENDED
A resultant force changes momentum.
F = Δp / t
Δp = change in
momentum
t = time taken
momentum
t = time taken
Impulse = F t = change in momentum (Δmv).
Spreading the change over a longer time gives a smaller force – the idea behind crumple zones and airbags.
Conservation of MomentumEXTENDED
With no outside force, the total momentum before a collision equals the total after.
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂u = velocity before · v = velocity after
Why It Matters · Safety Design
Impulse explains a lot of everyday safety design: lengthen the collision time to lower the force on people.
- Crumple zones and airbags lengthen the collision time, so the force on people is smaller.
- Catching a ball: pull your hands back to soften it.
- Seatbelts stretch a little for the same reason.
- A rocket pushes gas backwards to drive forwards.