Seesaws Flashcards
Center of mass
Equal mass on either side
Greater stability is achieved and balanced is improved
Lowering the center or mass and widening the base of support.
How does a balanced seesaw move?
It moves at constant angular velocity, because the seesaw has rotational inertia.
Angular position
an object’s orientation, angle and rotation axis from reference orientation.
Angular velocity
change in angular position with time, speed and rotation axis.
Torque
a twist or spin, amount and rotation axis twist or spin.
Why does a seesaw need a pivot?
To prevent translational motion
Pivot
placed at a natural pivot, center of gravity
Pivot allows rotation but not translation
Why does a lone seesaw rider plummet to the ground?
Torque on seesaw causes angular acceleration, the weight of a lone rider produces a torque, that torque would cause angular acceleration, seesaw’s angular velocity would change with time.
Angular acceleration
change in angular velocity with time, the rate and rotation axis change in angular velocity
Rotational mass
Measure of rotational inertia
Newton’s second law of Rotational Motion
An object’s angular acceleration is equal to the net torque exerted on it divided by its rotational mass. The angular acceleration is in the same direction as the torque.
Why do the riders’ weights and position matter?
Must balance seesaw-zero net torque
Adding a second rider adds a second torque
A rider’s torque is their weight times lever arm
Why does distance from the pivot affect speed?
Moving toward the pivot reduces rotational mass
Lever arm is a vector from pivot to rider
Moving toward pivot->faster angular accelerations
What twists does each rider experience?
2 torques - 1 due to gravity, 1 due to other riders
each rider experiences two torques about pivot
When seesaw balances, those torques sum to zero
rider exert equal but opposite torques on one another
