This lesson focuses on distance traveled by an input or output of a lever. Students focus on the feet of the cat and mouse. Whose feet can come closest to the ground? Whose feet go highest in the air? This one gets the longer ride. Then they figure out how to rearrange the cat and mouse so the other one gets the longer ride. Finally, they try to adjust the distances traveled when the directions are opposite.
- Mech-a-Blocks see-saws from previous lesson.
1. Observing cat and mouse on the same-direction see-saw: Demonstrate the same-direction see-saw from the previous lesson. See Figure 1.
Figure 1: Movement of the cat and mouse
- Do the cat and mouse go in the same or opposite directions?
- Is here a difference between how the cat moves and how the mouse moves?
- Who goes further, the cat or the mouse?
As you discuss the movement of cat and mouse, be careful to distinguish distance from direction. Two trips could have the same distance, but be in different directions. Two trips could be in the same direction, but with different distances. If a distance is more, we say one goes further. If it’s less, then the trip is not as far. One way to help children see that the mouse goes further than the cat is to trace their paths. Here’s how.
- If the other one wanted the better ride, what would you have to do?
2. Making the cat go further than the mouse: Distribute materials and present the challenge:
Make a see-saw so the cat goes further than the mouse.
Let children do a quick share with the class. As they show their see-saws, ask them what changes they made so the cat would go further than the mouse.
3. Different distances, different directions: Review the first see-saw they made. The cat and mouse went in opposite directions. Present the following challenge to the students:
Now the cat still wants to get a longer ride than the mouse, but this time in the opposite direction. Change your see-saw so this will happen.
Help children think about what they have to change to make the cat and mouse go in opposite directions. Once they have placed the cat and mouse on opposite sides of the fixed pivot, ask them to find out which one goes further. Here is a solution to the challenge.
After they have tried to solve this problem, review what they made. Test some of their see-saws to see if:
- The cat and mouse go in opposite directions; and
- The cat gets a longer ride.
If students have trouble seeing who gets the better ride, test it by tracing each ride.
4. Science Notebook
- Draw a see-saw that makes the cat go further than the mouse, in the same direction.
- Draw a see-saw that makes the cat go further than the mouse, in opposite directions.
- Students should learn that the further something is from the fixed pivot, the further it will travel.
Show students a see-saw like in Figure 4, where the cat and mouse go in opposite directions, the cat further than the mouse:
- How could I change this so the mouse goes further than the cat, still in opposite directions?
- How could I change this so the mouse goes further than the cat, but now in the same direction?