The seesaw

The seesaw

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The seesaw

Language: English
Description: This lesson allows the student to explore the balance of a seesaw. By adding weights to both sides the seesaw can be kept in balance when using different fulcrums. The relation between mass and distance from the fulcrum can be investigated and give an understanding about lever arms and moment of forces (torques). The example also opens for creating and working with balance scales.
Target: Key Stage 3
Category: Demonstration, Exercise
Discipline: Static forces, Gravity
Learning objectives:

Understand the relation between mass and distance to maintain balance of a seesaw. Understand the basic principles for a weight scale. Understand what a lever arm is and its relation to moment of force. Model a situation for balance and create an interactive simulation.

In class: Discuss balance of a seesaw.

How is it constructed and how does is look when no one is playing with it? What happens when kids of different sizes start playing it? Does it depend where they sit, how tall they are, what mass they have?

Discuss different aspects of playing with a seesaw in class and put up suggestions on the board. How can the centre of gravity of a seesaw be found? Discuss how this can be visualized and explored in Algodoo. Let the students create scenes in Algodoo using the suggestions you came up with together or let them use their own ideas. Help the students make decisions and ask guiding questions.

Encourage the students to follow the procedure Create – Predict – Interact – Evaluate.

Allow the students to follow-up and share their experiences in class after the simulation.

Steps in Algodoo


Create a scene

Create a plane. Create a seesaw with a fulcrum and a long rectangular box. Create objects with different sizes and densities and spread them on the seesaw. Or use the camera and take pictures of your friends and yourself.


Make a prediction

When is the seesaw in balance? How does the seesaw’s own mass influence balance?


Run/Interact

Start the simulation. Move the objects on the seesaw to make it balanced. Rotate the seesaw (if you have a computer with accelerometer, tilt the PC) and watch the trucks tip over and observe what happens.


Evaluate

What happens when an object is moved towards or from the fulcrum respectively? What is the relation between mass of the object and distance from the fulcrum? Relate the mass of the object to the normal force and gravity.
Seesaw.png


Suggestions for additional scenes

Modeling center of gravity, moment of force and lever arm.


Balancing book

When does the book fall off the table? Create a book sticking out from a table and find the critical point when the book falls to the floor.


Falling friend

What makes your friend fall with respect to centre of gravity? Take a picture of you friend, clean-cut and stand her on the floor. Tilt/rotate until she falls.


Weight scales

How is a simple scale constructed? Create a scale and use if for weighing different objects.
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