Using a Spring Scale to Measure Force
on an Inclined Plane

Objectives:

• Students will learn a ramp is a simple machine, the inclined plane.
• Students will become familiar with how an angle of an inclined plane(ramp) affects the force needed to move objects up the plane(ramp).
• Students will experiment to find how the use of an inclined plane(ramp) makes work easier.

Materials:

• Wooden toy car
• Board with a line marked off for stopping point about 4" from one end
• Two metric weights (secured to wooden car)
• Spring scale (board should be about 4" wide by 2' long)
• Experiment worksheet

Procedures:

1. Ask children if they have ever seen or walked up a ramp. Where? Is walking up a ramp easier than walking up stairs? Tell children the ramp is a simple machine. It is called an inclined plane.
2. Children should have already been introduced to the spring scale, how it works, and what it is used to measure. With the children in the group, briefly review what the spring scale is used for.
3. Have a child stack 4 textbooks on top of each other. Have another child place the board against the books on an angle, with the marked end up by the books.
4. Show children the wooden car and spring scale. Explain that they are going to use the ramp, car, and spring scale to measure the force it takes for the car to be pulled up the inclined plane they made.
5. Have another child attach the car(with the weights secured to it) to the spring scale. Have a child pull the car up the inclined plane by the spring scale. Have them keep pulling the car until the car reaches the marked line. Explain to the children this line is used so the results will be constant. Have another child look at the measurement of force used in ounces on the spring scale. Have all children record this number on the experiment worksheet.
6. Repeat procedures # 3-5, using 8, 12, and 16 textbooks. Have each child record the measurements for each experiment. Ask them if they notice anything about the measurements as the number of books increases an the ramp gets steeper.
7. Have children take turns doing different parts for each of the different stacks of books.
8. When using 16 textbooks, have the children record the force needed to pull the car up the inclined plane. Then have a child use the spring scale to pull the car up the top of the 16 stacked books without using the inclined plane. Have them record the results. Ask the children why they think the numbers are different.
9. Conclude with a review. It takes more force to move an object up a steep inclined plane than an inclined plane that is not as steep. Also, it takes more force to move an object to a higher level when you are not using an inclined plane.

Evaluation:

1. Can children make references to background knowledge of ramps. Can they connect with the lesson?
2. Are children recording the results for the different stacks of books? Are they making predictions as to whether the force needed will increase or decrease?
3. Were children able to understand why the force needed for each stack of books increased, and why not using the inclined plane required the most force? Did the children give any reasoning for this observation?