forces - car safety --> stopping safely

Question 1

how do brakes stop a car (friction force, brakes, wheel, kinetic energy)

Answer 1

when a force is applied to the brakes of a vehicle, they increase the force of friction between the brakes and the wheel. the work done by the friction force reduces the kinetic energy of the vehicle and the temperature of the brakes increase - since all the kinetic energy from the vehicle has been reduced, the car stops.

Question 2

what is stopping distance (not equation)

Answer 2

stopping distance is the distance it takes to react to a hazard -
it is the sum of the distance the vehicle travels during the driver’s reaction time and the distance it travels under the braking force.

Question 3

what is thinking distance

Answer 3

it is the distance the vehicle travels whilst the driver REALISES the hazard (reaction time)

Question 4

what is braking distance

Answer 4

it is the distance the car travels when the driver starts to brake to when the vehicle has stopped

Question 5

stopping distance equation

Answer 5

stopping distance = thinking distance + braking distance

Question 6

how do you test reaction time - explain

Answer 6

ruler drop

• person 1 will start a stopwatch and drop a ruler at the same time (person 2’s hand has to be hovering around the ruler)
• person 2 will try to catch it as quickly as possible once it is dropped
• as soon as person 2 has caught it, person 1 will stop the stopwatch
• the time shown is person 2’s reaction time

REPEAT FOR CERTAIN RESULTS

Question 7

things that affect thinking distance

Answer 7

• fatigue
• alcohol
• drugs
• distractions
• vehicle speed

Question 8

things that affect braking distance

Answer 8

• adverse road conditions (wet, icy, oily)
• adverse weather conditions (stormy, snowy, rainy)
• poor vehicle conditions (worn tyres, worn brakes)
• vehicle speed

Question 9

what are the two places kinetic energy can be transformed

Answer 9

in terms of collision - deforming in the crumple zone

in terms of deceleration - becoming heat in the breaks

Question 10

what do reaction times vary between

Answer 10

0.2 seconds –> 0.9 seconds depending on the person