Motion of vehicles Flashcards
what must happen in an emergency?
a driver must bring their vehicle to a stop in the shortest distance possible
equation for stopping distance:
stopping distance = thinking distance + braking distance
what is thinking distance?
the distance a vehicle travels in the time it takes for the driver to apply the brakes after realising they need to stop
what is braking distance?
the distance a vehicle travels in the time after the driver has applied the brake
factors that affect the driver’s reaction time? (4)
tiredness
drugs
alcohol
distractions
how do longer reaction times affect the thinking distance?
Longer reaction times increase the thinking distance when stopping from a given speed.
describe a way in which reaction time could be measured?
dropping a ruler between someone’s open thumb and forefinger
factors that affect braking distance: (3)
-poor road and weather conditions
-poor vehicle conditions
-mass of the vehicle
give an example of poor road conditions:
gravel, or wet or icy roads
give an example of poor vehicle conditions:
worn brakes or worn tyres
give an example of an increase in mass of the vehicle:
extra passengers
how do poor road and weather conditions affect the braking distance?
less friction between tyres and the road
how do poor vehicle conditions affect the braking distance?
less friction between brakes and wheels
how does the mass of the vehicle affect the braking friction?
the braking friction has to work for a greater distance to remove the larger kinetic energy
what happens when a force is applied to the brakes of a vehicle? and how does this effect the kinetic energy of the vehicle + other vehicle components?
-there is work done by the friction between the brakes and the wheel.
-this reduces the kinetic energy of the vehicle, slowing it down and causing the temperature of the brakes to increase.
what is the correlation between the speed of the vehicle and the braking force?
The faster a vehicle travels, the greater the braking force needed to stop it in a certain distance will be
what does a greater braking force produce?
A greater braking force produces a greater deceleration.
why are large decelerations dangerous? (2)
- may cause the brakes to overheat,
-the driver may also lose control of the vehicle.
what is the thinking distance proportional to?
and why? (explain)
-thinking distance is proportional to the starting speed.
-because the reaction time is taken as a constant, and distance = speed × time.
what does the braking distance increase by every time the starting speed doubles? and why?
-the braking distance increases four times each time the starting speed doubles.
-this is because the work done in bringing a car to rest means removing all of its kinetic energy.
which type of energy is work?
Work done = kinetic energy
considering that work is a force, how can it be implemented in an equation?
Work done = braking force × distance
state the equation that links work and KE?
F x D = 1/2 x m x v^2
if
stopping distance = thinking + braking distance
which equations could be used to deduce the stopping distance?
thinking distance:
D = S x T
braking distance:
D x F = 1/2 x M x V^2
