IGCSE 0625 · MECHANICS · 1.6

Momentum

Momentum, impulse, and conservation of momentum, with the everyday safety design they explain. An Extended sub-topic that builds on motion and forces.

TOPIC 1.6: MOMENTUM CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 1.2 Motion 1.5 Forces LEADS TO Collisions & safety Vehicle design MOMENTUM EXTENDED 1 · MOMENTUM Momentum measures how hard it is to stop a moving object. p = m v p = momentum (kg m/s) It is a vector: direction matters. More mass or more speed means more momentum. 2 · FORCE & IMPULSE A resultant force changes momentum. F = Δp / t Impulse = F t = change in momentum (Δmv). Spreading the change over a longer time gives a smaller force. That is the idea behind crumple zones and airbags. 3 · CONSERVATION OF MOMENTUM With no outside force, the total momentum before equals the total after. m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂ before after they move off together 4 · WHY IT MATTERS Impulse explains a lot of safety design. 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.
TOPIC 1.6: MOMENTUM CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 1.2 Motion 1.5 Forces LEADS TO Collisions & safety Vehicle design MOMENTUM EXTENDED 1 · MOMENTUM Momentum measures how hard it is to stop a moving object. p = m v p = momentum (kg m/s) It is a vector: direction matters. More mass or more speed means more momentum. 2 · FORCE & IMPULSE A resultant force changes momentum. F = Δp / t Impulse = F t = change in momentum (Δmv). Spreading the change over a longer time gives a smaller force. That is the idea behind crumple zones and airbags. 3 · CONSERVATION OF MOMENTUM With no outside force, the total momentum before equals the total after. m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂ before after they move off together 4 · WHY IT MATTERS Impulse explains a lot of safety design. 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.
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