Flashcards in FM1 - Stopping distance and momentum + collision Deck (21):
What is the stopping distance of a car?
The distance covered in the time between the driver first spotting a hazard and the car coming to a complete stop
What is the distance it takes to stop divided into?
The thinking and braking distance
What is the thinking distance of a car?
The distance the car travels between the driver noticing the hazard and applying the breaks
What two factors affect the thinking distance?
1) How fast you're going
2) How tired you are - tiredness, drugs, alcohol and old age can affect your reaction time
What is the braking distance?
The distance the car travels during deceleration whilst the breaks are being applied
What four factors affect the breaking distance?
1) How fast your going - the faster your going, the further it takes to stop
2) The mass of the vehicle - the larger the mass, the longer it takes to stop
3) How good your brakes are - should be checked regularly
4) How good the grip is - depends on road surface, weather conditions and tyres "aquaplaning"
How can bad visibility be a major factor for incidents?
Lashing rain, thick fog and bright upcoming lights might mean that the driver doesn't notice a hazard until they're quite close having a shorter distance available to stop in
What is momentum?
A vector quantity
What is the equation for momentum?
Momentum (kg m/s) = Mass(kg) x Velocity(m/s)
The greater the mass of the object, the greater the velocity...
The more momentum
What does momentum before equal?
Why does momentum before = momentum after?
Momentum is conserved when no external forces act f
When working out momentum questions what should you always label the directions with?
Positive and negative
What do forces cause?
Changes in momentum
A large force means...
A faster change in momentum (greater acceleration)
What is the equation linking force, momentum and time?
Force (N) = Change in momentum(kg m/s) /time taken(s)
Give an example of when momentum changes very quickly
In a car crash - the forces on the body are very large and are more likely to cause injury
Why are cars designed to slow people down over a longer time when they crash?
The longer it takes for a change in momentum, the smaller the force and so the less serve the injuries will be
How does a crumple zone in a car slow down momentum?
Increases time taken for the car to stop
How do seat belts in a car slow down momentum?
They stretch slightly increasing the time taken for the wearer to stop. This reduces the forces acting on the chest h