Rotational Motion

Rotational or angular speed (velocity): Linear speed traveling along a circular path

Tangential Speed

At the axis, the tangential speed is …

None, there is only rotation

As the distance from the axis of rotation increases, the tangential speed increases, because…

You cover a greater distance in the same amount of time (but rotational speed is the same)

Rotational Inertia

Based on mass and distance (of mass) from the axis of rotation

Torque

Torque = force × lever arm distance

Torque formula

T = FsinΘ × r

You get less torque at anything other than

90°

A longer arm produces …. Torque

Greater torque

Problem with longer arm: added mass increases

Rotational inertia

Trebuchet provides added length without a huge increase in mass, how?

With the sling

Center of mass (COM) / Center of gravity (COG)

Balance point

The balance point of COM / COG is the point at which

The point an objects rotates around

Stability: for an object to be stable…

You want a low center of mass and a wide base of support

Centripetal force

The actual force that causes you to follow a circular path

Centrifugal Force

What you feel (own inertia)

If there was no force (centripetal), the object would …

Take off in a straight line (due to inertia)

Again, what’s the result of centrifugal force?

The result of your own inertia

Stimulated Gravity

You can do so..

Formula for Centripetal Force

F© = mv² / r

Angular momentum (L)

Mass × velocity × radius = mvr

Conservation of Angular Momentum

Just like linear momentum, momentum before has to be equal to momentum after for this

Rotational Inertia formula (I)

Mass × radius

Rotational velocity (w)

Velocity

Law of Conservation of Angular Momentum (ex

lw(before) = lw(after) (cat falling