Forces Flashcards
What is the stopping distance
The minimum distance required to stop a vehicle in emergency
the stopping distance is = to
stopping distance +thinking distance
what is the thinking distance
time between the driver seeing the hazard and applying the brakes
what affects the thinking distance and what physical conditions affect these factors
speed of vehicle- the faster the further you will travel
reaction time -things like tiredness/drunk/drugs
what is braking distance
distance taken to stop under braking force
what affects braking distance
speed and mass which increase kinetic energy which must be 0 for vehicle to stop
-condition of brakes
-traction between car and road
-condition of tyre thread which grips wheels on road
momentum(P) equation
momentum(KG/M/S)=mass(kg) x velocity(m/s)
P=mv
what happens to momentum in a closed system
momentum before=momentum after
in a gun the momentum of the bullet initially is 0. Why is this and explain what happens to counteract this
The bullet will have a momentum in the forward direction so the gun recoils backwards so guns momentum+bullets momentum=0
what is the equation for a force used to accelerate an object
mass xchange in momentum/change
in time
mv-mu/t
what happens to momentum in a car crash
momentum will decrease to 0 almost instantly
how do we reduce the chance of head trauma or spinal injuries in car crashes
spread change in momentum over longer space of time to reduce force
3 ways we can get cars to lose momentum
crumple zones
seatbelts
airbags
explain how these 3 safety features work
crumple zones-at the front and back of the car and crumple on impact so there is small extra time for car to lose momentum as it crumples
seatbelts-prevent you from flying out of the car as it stops/stretchy so you slow down slower
airbags-more compressible unlike dashboard and help lose momentum slower
what do the 3 safety features cars have help do
they increase the time taken for momentum to be lost so lower force so less chance of injury
