stopping distance in vehicles, braking

what two distances make up the stopping distance?

the thinking and braking distance

What things can make the stopping distance greater?

If at a higher speed

What is the thinking distance?

the distance travelled during the driver’s reaction time

What can increase the reaction time of a driver?

• Being tired

• Being under the influence of drugs/alcohol

• Distractions, like mobile phone

What things can affect the braking distance of a vehicle?

• Wet or icy conditions reduce friction between the tires and road, increasing distance

• Worn tires also reduce friction

• The size of the braking force - braking harder causes a large force which acts to decelerate the car

What’s the equation for kinetic energy here?

Ek = 0.5 x mass x velocity²

What would happen to the kinetic energy if the velocity doubled?

Because the velocity is squared in the equation for Ek, the kinetic energy would quadruple.

What force acts when the brakes are pressed?

The brake presses against the wheel, causing friction between the brakes and wheels

When the car slows and loses kinetic energy while braking, where does this kinetic energy go?

It is converted to thermal energy, which causes the brakes to heat up due to the friction between the wheel and brakes and the temperature increases

How much force is needed to be applied to brake a car?

The higher the speed the car travels, the greater the braking force needed

What can happen if the driver brakes hard at a high speed?

the brakes can overheat or the driver can lose control

how can you calculate the forces involved in deceleration?

force = acceleration x mass

State the equation involving velocity, acceleration and time

v-u / t = a