Energy systems
Invent-a-Wheel
3. Ramps and Sleds
Overview
Students explore how putting an object on a ramp can get it to move “by itself,” how to prop up the ramp with a stand, and how ramp height affects whether or not it will move. The lesson ends with an experiment: predict and then test to find the smallest ramp height that will make the sled go down.
Here is another video on how to make the ramp stand.
Procedure
-
Class meeting: Ask students if they have ever been on a sled, or seen one on TV:
- What is a sled? What does it do?
- What makes it go downhill?
-
Make a sled: Provide large cardboard sheets and small rectangles. Ask students:
- Find a way to make the small piece work like a sled.
-
Propping up the ramp: By now, students should have figured out how to use the ramp to make the sled go down. However, they may be holding up one end of the ramp themselves. Ask:
- Find a way to make the ramp stand up without touching it.
- Encourage students to find objects they could use to prop it up.
- In discussion, the term “gravity” may come up. If not and after getting students’ language to describe gravity, say we call that “gravity.” Describe gravity as a force that pulls things down (toward the ground).
-
The ramp stand: The objects students use to prop up the ramp may not be stable. Also they are all different, making it hard to tell how high the ramp is. Provide each student with a ramp stand template and a ramp with slits. Show students how to fold the stand and assemble it with the ramp. (Here is a video on making a ramp stand. Directions for making a ramp are included in Lesson 10 as an example of a “How-to Book”) Ask:
- What do you see that is printed on each stand?
- How could we use these numbers to decide how high the ramp is?
- What will make the sled go down?
- Demonstrate a ramp that is adjusted to a height of 1 ″ on the stand. Ask students to predict if sled will slide down. Then demonstrate that it doesn’t:
- Why won’t the sled go down?
- What would you need to do to the ramp to make the sled go down?
-
An experiment: How high does the ramp need to be? Introduce what it means to do an experiment. First we make a prediction. Then we test the prediction to see if we were right. After the experiment, we write down what happened.
- Predict how high you think the ramp needs to be for the sled to slide. Circle this height in blue on the worksheet.
- Tally individual predictions on a class chart, keeping track of who predicted each height
- Make the ramp the height you predicted. Does it work? Does it slide at all?
- Adjust the ramp so the sled just starts to slide. Mark this height in red.
- What did you notice? Fill in the blanks on the worksheet.
-
Outcomes
- Students learn to make and use a ramp, as a way to get the sled to go down by itself.
- Students explore how ramp height affects whether the sled will go down.
- Students learn to do an experiment. First they predict the minimum ramp height that will make the sled go down, and then they test their predictions.