Inclined Planes: Making Lifting Easier

When the ancient Egyptians were building the pyramids, they created ramps to help them move gigantic blocks of stone to the upper levels. A ramp is a type of simple machine called an inclined plane. These flat, sloping surfaces make moving objects from one height to another easier. Inclined planes do not reduce the work done, but they do reduce the force required. In this activity you will find out how an inclined plane affects the force required to move a block.

Materials

Spring scale (calibrated in Newtons); Masking tape; Wooden block; Stack of several books; Two pieces of cardboard of different lengths (for example, a twelve-inch piece and a sixteen-inch piece); Metric ruler

Activity

1. Stack several books on top of each other on a table. Measure the height of the books in meters. Make a note of the height.
2. Use masking tape to attach the wooden block to the hook on the spring scale. Once they are securely attached, pull on the scale to lift the block to the same height as the top of the stack of books. Read the force (number of Newtons) required to make that lift. Make a note of this force.
3. Select the shorter piece of cardboard and prop one end on the edge of the book stack to form a ramp. Now use the spring scale to pull the same block slowly up the ramp. Note the force required to make this pull.
4. Repeat step 3 using the longer piece of cardboard and note the force required to make the longer pull.

Follow-Up Questions

1. How did the force required to lift the block straight up compare with the force required to pull the block up the first ramp?
2. Judging from your data, how does increasing the length of a ramp influence the amount of force needed to move an object from one height to another?

Answers

1. Less force was needed to pull the block up the ramp.
2. Increasing the length of the ramp reduces the force needed.

Extension

Predict how much force would be required to lift the block if you used a piece of cardboard exactly one-half the length of the shorter piece. Cut the shorter piece in half and see if your prediction was correct.