Changing momentum

L.O.: Calculate the change in momentum caused by a force.

Car Crash Safety!

How Can We Reduce the Effects of Collisions?

• IP 4.13 video

Old-fashioned seat-belts could cause damage like this. Modern “inertia-reel”

belts stretch slightly before locking

• If a car has a collision when it is has a certain momentum, the force the driver feels will be reduced if you can make the time the crash lasts for longer.

It looks like a very bad crash. Twisted It looks like a very bad crash. Twisted metal and broken glass and yet the metal and broken glass and yet the

passengers walked away from this one. passengers walked away from this one. How?How?

Notice that the passenger compartment is not damaged. Why?

Again, the impact area collapses but the passenger area remains intact.

Crumple Zones

• Regions around a vehicle which are made weak deliberately.

• They increase the impact time and so lessen the impact force

What difference does a Crumple Zone Make?

0

2

4

6

8

10

12

14

16

18

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

Time (s)

Vel

ocit

y (m

/s)

Car without Crumple Zone

Car with Crumple Zone

To do:

1)Workbook page 71

1) momentum worksheet

Changing momentum

L.O.: Calculate the change in momentum caused by a force.