What You Need:
- Several large books
- Spring scale (a scale used to measure force)
- Small toy car or truck
- Board about 18 inches (45 cm) long
- Plastic bag filled with rice to use as a weight
What You Do:
- Stack the books on the table near the table's edge. Lean the board on the table against the books to create a ramp.
- Place the weight on the table against the bottom of the ramp. Use the spring scale to drag the weight up the ramp. Have an adult help you read the scale.
- Place the weight on the table and lift it to the same height as in step 2, using the spring scale. What does the scale read now?
- Balance the weight atop a small toy car or truck. Use the spring scale to drag the weighted toy up the ramp. Was it easier to drag the weight on wheels?
- Add or take away books to raise or lower the ramp. Does this change the effort you have to make to lift the weight?
It was the same amount of work, but it was easier to drag the weight up the ramp than to lift it straight up. On wheels, the work is even easier, because the wheels reduce friction. The lower the stack of books (the more flat the ramp), the less force is needed to move the weight. A higher stack of books (a steeply sloping ramp) means you must use greater force to move the object.