Physics 
Lesson
18: Car crash safety! 
Curriculum
Key: 
Present
in Additional Science specifications 
Objective(s)
1.
Know several devices designed
to promote safety in the event
of a car crash.
2. Understand that these devices
work because they increase the
time of an impact.
3. Understand that increasing
the time of an impact reduces
its force.

Resources
needed
PowerPoint
Graph paper. 
Starter:
15
minutes Use
PowerPoint slides to promote class
discussion about safety features
(crumple zones, inertiareel seat
belts, airbags). 
Teacher
input/assessment
Steer
discussion towards what about
the collision is changed by the
safety feature (e.g. time of impact,
area of force). 
Main
Activity 1: 20
minutes Students
plot graphs of velocity versus
time for the two collisions and
answer questions. If time is short
the next slide gives graphs. A
version which requires calculations
is available for higher ability
students. 
Teacher
input / assessment
May
need to remind students that acceleration
is the gradient of v – t graph. 
Main
Activity 2: 15
minutes Students
annotate outline diagram of car
with various safety features.
For each feature they must explain
how the force on the passengers
is reduced (i.e. by increasing
the area of impact or increasing
the time of the impact). 
Teacher
input / assessment
Circulate
and prompt. Some safety features
are about prevention (e.g. hazard
lights) but less able students
should be encouraged to include
these. 
Plenary:
15
minutes Use
the untitled/unlabelled graphs
as the basis for discussion. Given
some simple graphs (see attached
graph sheet or last slide of PowerPoint)
ask the students to describe what
the graphs show. 
Teacher
input / assessment
For
lower ability students the teacher
could add some X and Y axis labels
(e.g. distance and time, or comedy
ones like number of drinks and
visits to the toilet). The teacher
could lead a group discussion.
For higher ability students the
teacher could ask them to apply
their own labels for the X and
Y axes and decide what the graph
is saying. 
Learning
Outcomes: All
students must: understand
that many car safety features
work because they reduce forces.
Most
students should: explain
how the features reduce forces.
Some
students could: calculate
the size of accelerations and
forces give the relevant data. 
Key
Skills: interpreting
graphs, understanding reciprocal
relationships Key
words: acceleration,
deceleration, force
Homework:
Investigate
the ‘g’ forces experienced by
astronauts on takeoff. 
Differentiation:
More
able: Can
calculate accelerations and forces
from data or graphs.
Less
able: Can
describe safety design features
and explain that they work by
reducing forces. 