# Heave Ho!

## Learning Objectives

Students will investigate the use of an inclined plane to make it easier to lift a heavy object.

Movement

## Materials

Each group needs:

• 1 spring scale
• Any hard, flat plane (plank of wood, stiff cardboard, etc.)
• Items to measure (bag of marbles, stones etc.)
• Stack of books or blocks to prop up one end of plane

## Introduction/Motivation

This activity provides an illustration of how a simple machine, in particular the inclined plane, is used to make life easier. An inclined plane is a slope that allows a load to be raised gradually with less effort than lifting it straight up. The angle of the plane is important: the steeper the incline, the more effort required whereas a more gradual slope will require less effort.

A spring scale is a device used to measure how much something weighs. When an object hangs from the hook at the bottom of the scale, the needle or plunger moves up and down depending on the weight of the object. The needle will line up with one of the numbers representing the apparent weight of the object. If you don’t have any spring scales in the classroom, they are available at Scholar’s Choice for about \$7 a piece. You can also try a hardware store.

## Procedure

Before starting this experiment, show the class the spring scale and demonstrate how it works. It may also help to have the inclined planes set up at an angle of inclination of 30 to 45 degrees. The higher the incline, the less obvious the effect will be.

Have students measure how heavy a bag of rocks would be by lifting it straight up. While one student is holding the scale, the other can help read and record the number on the worksheet under the appropriate heading. Then have students drag the same bag of rocks up the incline (with the scale attached) and record that number in the chart under the appropriate heading. See figure 1.

Figure 1: Measuring weight using spring scale

Students can regroup as a class to discuss the results of their experiment. The conclusions can be filled out in their worksheet.

## Further Investigations

Time permitting, you could also have the students investigate the effect of the slope angle, qualitatively. With the same object measured previously, repeat the scale reading while lifting the object up the incline with a smaller or larger slope.

## Investigating Questions

• What are some examples of inclined planes?
• Why use inclined planes?
• What would happen if we made the slope steeper?
• Can anyone think of a way to make it even easier to move the object up the incline? (Answer: Add wheels, possible idea for further investigation/measurements)