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Momentum (Stopping Distances (Thinking Distance: time to react (Increased…
Momentum
Stopping Distances
Thinking Distance: time to react
Increased if:
Vehicle is travelling faster
Driver's reaction is slower, eg:
Drink-driving
Tiredness
Poor visibility
Fog
Braking distance: time between applying the brakes and vehicle stopping
Increased if:
Vehicles is travelling faster
Brakes are worn
Tyres are in poor condition
The car has a greater mass
Road is wet/icy
Stopping Distance = Thinking Distance + Braking Distance
Safety Features in Vehicles
Change in momentum = Force * time
To bring a vehicle to a complete stop, you can apply:
a large force over a short period of time
a small force over a large period of time
:. to minimise force experienced by the passenger, the time of the collision is increased
Use crumple zones, airbags etc.
Conservation of Momentum
The momentum of a system is conserved providing no
external resultant
force acts upon it
Car collision
mu
[a]
+ mu
[b]
= mv
[a]
+ mv
[b]
Momentum (kgm/s) = Mass (kg) • Velocity (m/s)
p = mv
Resultant Force = Change in Momentum / Time
F = (mv-mu)/t