Students think about how the dump truck might be made to negatively accelerate or slow down. They use what they know about friction force to modify the truck-and-ramp system. Student groups test ideas for reducing the speed of the dump truck as it travels the ramp.
Materials (per student group)
- 1 dump truck
- rubber bands
- sand paper
- paper towels
- 1 pc. stiff cardboard (30 cm x 60 cm)
- 1 meter stick
- 1 watch with a second hand or timer
- masking tape
- activity sheet
Leading the Activity
Engage students in a review discussion of the speed data collected in the dump truck and ramp activity. Ask student groups to discuss what they know about friction and how friction affects the motion of an object. Show them the materials that can be used in the activity. Invite student groups to brainstorm ideas for reducing the speed of the truck as it travels the ramp. Challenge them to predict which material will work best at affecting the speed of the truck. Invite student groups to modify the truck-and-ramp system, test and record the results.
- Use the cardboard and the books to construct a ramp 20 cm in height.
- Tape the bottom of the ramp in place.
- Hold the dump truck at the top of the ramp with the rear wheels even with the cardboard edge.
- Release the truck; time and record how long it takes for the truck to reach the end of the ramp. Do three trials.
- Calculate and record the speed of the truck. (distance divided by time = speed)
- Predict and select the material that will work best at increasing the friction and reducing the speed of the truck as it travels the ramp.
- Prepare the modifications to the truck-and-ramp system.
- Repeat steps 4 and 5.
- Discuss and record your conclusions.
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