Speed and crumple zones worksheet other worksheets
for use with the Speed: no crumple zones / crumple zones simulation
from the materialworlds Crash simulations
© materialworlds.com 2002

In these simulations two cars crash into a wall - the fast car at twice the speed of the slow.
In the first simulation the cars don't have crumple zones, in the second they do.
The cars are of equal mass.

This worksheet explores the different effects of doubling the crash speed in cars with and without crumple zones.

The collision simulations automatically repeat. Pause a simulation to examine a particular moment. Adjust the "Time" control to slow the simulation to study particular events in fine detail. To examine the graphs, pause the simulation once the collisions are over, then click on the links for the different graphs.

First run the simulation without crumple zones.

1. What similarities and differences are there between the fast and slow collisions (the faster is at twice the velocity of the slow)?
Comment on the timing of different phases of the collision, on the ways and the amount each car is distorted, and on the passenger compartment acceleration graph.

2. The diagram diagram accompanying this worksheet collects all the graphs together, and adds vertical lines representing a series of moments through the collision. In answering this question you may find it useful to slow down and pause the simulation - matching the movement of the cars to the graphs as they are drawn.
Describe what's happening (to the cars without crumple zones) at each of the moments i  ii_nc and iii_nc  (the subscript _nc means "no crumple") mentioning each car's position, shape and state of motion:
a) (i)
b) (ii_nc)
c) (iii_nc)

3.
a) How do the pre-collision kinetic energies of the fast and slow cars compare?
b) Is this what you would have expected, and why?

4.
a) What parameter (tracked in one of the graphs) can be assumed to vary proportionally to the stopping force on each car?
b) Why?

5.
a) How do the stopping forces on the slow and fast cars compare (in the period i to ii_nc)?
b) How do the changes in kinetic energy of the slow and fast cars compare (in the same period i to ii_nc)?
c) How can this difference in stopping forces (5a) account for the different changes in kinetic energy (5b)?


Now run the simulation with crumple zones.

6. What similarities and differences are there between the two collisions (the faster is at twice the velocity of the slow)?
Comment on the timing of different phases of the collision, on the ways and the amount each car is distorted, and on the passenger compartment acceleration graph.

7. Looking again at the diagram accompanying this worksheet, describe what's happening to the cars with crumple zones at each of the moments i  ii_c and iii_c  (the subscript _c means "crumple") mentioning each car's position, shape and state of motion:
a) (i)
b) (ii_c)
c) (iii_c)

8. Remembering your answer to question 4,
a) How do the stopping forces on the slow and fast cars compare (in the period i to iii_c)?
    (make sure you comment on how the forces vary with time)
b) How do the changes in kinetic energy of the slow and fast cars compare (in the same period i to iii_c)?
c) Explain how this difference in stopping forces (and how they vary with time) (8a) accounts for the different changes in kinetic energy (8b)?

Compare the collisions with and without crumple zones.

9. What difference does a crumple zone make to how a car slows in a higher velocity collision?

10. What are the effects of this
a) on the car?
b) on the passengers?