• Activity
  • Roads, Vehicles & Traffic

Forces and road crashes

Learning areas:
  • Maths
  • Science
Year levels:
  • Year 5
  • Year 6

Students investigate what happens when forces move, stop or change the direction of something which is already moving. They look at what happens to vehicles and passengers when such forces come into operation.

Students can use the Forces and people in a crash’ worksheets to guide their investigation.

Materials

Each group of students will need:

  • Stiff piece of cardboard, about 50cm long, for a ramp
  • Base for ramp (to raise ramp about 10cm)
  • Small car
  • Block of wood
  • Sticky tape
  • Ruler
  • Small toy person

Instructions

  1. Mark off 10cm intervals along the ramp, up to 50cm.
  2. Set up the equipment as shown in the diagram and hold the car on the 10cm mark from the base of the ramp.
  3. Release the car from the 20, 30 and 40cm marks in turn and record observations.

  1. Tape a block securely about 20cm from the bottom of the ramp.
  2. Sit the toy person on the car.
  3. Place the car at the 10cm mark and release.
  4. Measure the ‘impact distance’ – how far the toy person lands from the car.
  5. Repeat for the 20, 30, 40 and 50cm marks and record the impact distance each time.
  6. Repeat this for each distance 2 more times. Work out the average impact distance for each height on the ramp.

Discussion questions

  • What forces cause the car to move?
  • How did the impact distance change when the   car was released in different places along the ramp?
  • What do you think happened to the impact speed   of the car as it was released from positions higher up the ramp?
  • When the ‘person’ is thrown from the car, what   direction does it travel in? Why?
  • How is the distance the ‘person’ is thrown   related to the car’s impact speed?
  • What does this experiment tell us about the   role of speed and the impact that a crash has on our body.
  • How could forces be reduced in the event of a crash?

Information for teachers

About forces

Forces are in operation all around us. They operate in pairs and if the forces are balanced, the object will either remain at rest, or continue moving at a steady speed in a straight line. If one force is greater than the other, the object will either speed up, slow down or change direction. The greater the force, the greater the damage.

The forces acting on the toy car in the experiment include:

  • Gravitational force –pulls objects towards the   centre of the earth. This causes the car to roll down the ramp.
  • Frictional force – resistance caused by the   wheels of the car rubbing against the cardboard and the air against the car.
  • Applied force – the block applies a force on   the car to stop the car.

When an object is in motion, it has momentum. If it comes to a sudden stop (like when the toy car hits the block), people in the car will continue at the same momentum until a force stops them. The force could be from gravity, a seatbelt, an airbag or a windscreen.

The formula for momentum is: Momentum (kg m/s) = mass (kg) × velocity (m/s)

In the experiment, the car will gain more velocity the higher it starts on the ramp (gravity is acting on it for longer). The more velocity the car has, the more momentum the toy person will have when the car hits the block and the further the toy person will be carried after impact.

Forces and car crashes

The outcome of a crash (that is, the severity of injury or damage) depends on the forces generated at the moment of contact:

  • The faster a vehicle travels, the less time it   has to stop
  • The faster the two objects collide, the more   force will be generated
  • The more force that is generated, the more damage is done to the human body and other objects in the collision.

Victorian curriculum

Science

Level 5 & 6

Construct and use a range of representations, including tables and graphs, to record, represent and describe observations, patterns or relationships in data (VCSIS085)

Maths

Level 5

Pose questions and collect categorical or numerical data by observation or survey (VCMSP205)

Construct displays, including column graphs, dot plots and tables, appropriate for data type, with and without the use of digital technologies (VCMSP206)

Describe and interpret different data sets in context(VCMSP207)

Level 6

Solve problems involving the comparison of lengths and areas using appropriate units (VCMMG224)

Construct, interpret and compare a range of data displays, including side-by-side column graphs for two categorical variables (VCMSP235)