This practical involves the principle of speed and how a moving vehicle can be slowed rapidly by increasing the level of frictional force acting upon it.
Standard physics trolleys can be made to travel down a long ramp and into a tray of sand. The mass of the trolley, inclination of the ramp and depth of sand can be variable factors in this practical. The average speed of the trolley can be calculated using the formula below:
Speed = Distance/Time
Students can calculate how far the trolley has travelled once it reaches the sand. The deeper the sand, the greater the force of friction on the trolley and the sooner it will stop. Increasing the mass of the trolley (by adding masses) may also mean the trolley travels further.
Equipment required (per set):
- Standard physics trolley
- Long ramp (approx 1.5-2.5m)
- Tray
- Quantity of sand enough to fill the tray
- Metre rules
- Additional masses
Smaller toy cars can be used instead of the trolleys however the fact they are much lighter may not allow them to travel through the sand far enough to be accurately measured.
Real sand traps are sometimes located next to roads on steep hills. Cars or lorries can decrease their speed quickly in an emergency by driving into the sand.