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2.1 Seesaws

# 2.1 Seesaws - Observations About Seesaws • • • •...

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1 Phy 1405 1 Key Concepts: 1. Rotational Inertia 2. Angular Velocity 3. Torque 4. Center of Mass 5. Moment of Inertia (rotational mass) Phy 1405 2 Observations About Seesaws A balanced seesaw can remain horizontal A balanced seesaw rocks back and forth easily Two equal-weight children balance a seesaw Two unequal-weight children don’t balance But moving the heavy child inward helps Phy 1405 3 Question 1 How exactly does a balanced seesaw behave? – Is a horizontal seesaw balanced? – Is a balanced seesaw horizontal? Phy 1405 4 Physics Concept Rotational Inertia – A body at rest tends to remain at rest – A body that’s rotating tends to keep rotating Phy 1405 5 Physical Quantities Angular Position – an object’s orientation Angular Velocity – its change in angular position with time Torque – a twist or spin Angular Position 2 π radians in a full circle Axis of Rotation Angle of Rotation Phy 1405 6 Newton’s First Law of Rotational Motion A rigid object that’s not wobbling and that is free of outside influences rotates at a constant angular velocity. A rigid object that’s not wobbling and that is free of outside torques rotates at a constant angular velocity.

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