5.4 Braking and collisions

5.4 Braking and collisions
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Slide 1: Slide
NatuurkundeMiddelbare schoolhavo, vwoLeerjaar 2

This lesson contains 20 slides, with interactive quizzes and text slides.

time-iconLesson duration is: 30 min

Items in this lesson

5.4 Braking and collisions

Slide 1 - Slide

In traffic you always have to able to stop in time without having a collision.

Slide 2 - Slide

What factors will influence the braking distance?
A
Mass of the car
B
Braking force
C
Speed of the car
D
All answers above

Slide 3 - Quiz

The higher the initial speed,
the longer the braking distance.

Slide 4 - Slide

The greater the mass of the vehicle,
the longer the breaking distance.

Slide 5 - Slide

If the road is slippery you have to brake slowly, othewise the car will slip.

Slide 6 - Slide

Braking distance

Depends on:

  • Initial speed;
    the faster you are going, the greater the braking distance
  • Total mass;
    the greater the mass the greater the braking distance
  • Braking force;
    the harder the brakes are pressed the shorter the braking distance

Slide 7 - Slide

Stopping distance = reaction distance + braking distance

Slide 8 - Slide

Reaction distance

Reaction distance  =  reaction time  x  velocity

The reaction time in normal conditions is around 1.0 second.

Slide 9 - Slide

Braking distance
Reaction distance

Slide 10 - Drag question

A horse runs to the finishline at 39.6 km/h. The drivers reaction time is 0.2 s. The braking distance is 22.8 m. Determine the stopping distance.

Formulas:
stopping distance = reaction distance + braking distance
reaction distance = reaction time x velocity

Slide 11 - Slide

A horse runs to the finishline at 39.6 km/h. The drivers reaction time is 0.2 s. The braking distance is 22.8 m. Determine the stopping distance.

Slide 12 - Open question

  v = 39.6 km/h = 11 m/s (39.6 / 3.6)
  t = 0.2 s (reaction time)
  braking distance = 22.8m 

stopping distance = reaction distance + braking distance

reaction distance = v x t = 11 x 0.2 = 2.2 m
           stopping distance = reaction distance + braking distance
           stopping distance = 22.8 + 2.2 = 25m

Slide 13 - Slide

initial speed and braking distance
If the speed is n times bigger, 
the braking distance becomes n2 times longer.
v = 10 m/s
s = 5 m
v = 20 m/s
s = 20 m
v = 30 m/s
s = 45 m
n= 2= 4
braking distance = 4 * 5 = 20 m
n2 = 32 = 9
braking distance = 9 * 5 = 45 m

Slide 14 - Slide

Slide 15 - Slide

If the initial velocity is 10 m/s the braking distance is 5 m. What is the braking distance with an initial velocity of 90 km/h?

Slide 16 - Open question

If the initial velocity is 10 m/s the braking distance is 5 m. What is the braking distance with an initial velocity of 90 km/h?

v = 90 km/h = (90/3.6) m/s = 25 m/s
n = 25/10 = 2.5
n= 2.52 = 6.25
braking distance = n2 x old braking distance 
braking distance = 6.25 x 5
braking distance = 31.25 m

Slide 17 - Slide

If the initial velocity is 10 m/s the braking distance is 5 m. What is the initial velocity with a braking distance of 80 m?

Slide 18 - Open question

If the initial velocity is 10 m/s the braking distance is 5 m. What is the initial velocity with a braking distance of 80 m?
braking distance = 80 m
braking distance = n2 x old braking distance 
80 = n2 x 5
n2 = 80 / 5 = 16
n = √16 = 4
initial velocity = 4 * 10 = 40 m/s

Slide 19 - Slide

Homework
finish chapter 5

Slide 20 - Slide