Physics of Rotational Motion

Flashcards covering key concepts and definitions related to rotational motion and forces.

Axis

An invisible line that an object spins around.

What is the difference between a “Rotation” and a “Revolution”?

Rotation = spins around itself.
Revolution = moves around something else.

Rotational speed

How fast something spins (turns per second).

ω (omega)

The symbol for rotational speed.

What is the unit for rotational speed?

Radians per second (rad/s) or RPM

How does rotational speed change as the radius changes?

It stays the same — radius does not affect rotational speed.

Tangential (linear) speed

The actual speed of a point on the edge of a spinning object.

The symbol for tangential (linear) speed.

v

The unit for tangential (linear) speed.

Meters per second (m/s)

How does tangential speed change as the radius changes?

It increases as radius increases.

How are tangential speed and rotational speed related?

Tangential speed = rotational speed × radius (v = ωr).

How are tangential speed and radius related?

Directly related-Bigger radius = faster tangential speed

What does RPM stand for?

Revolutions Per Minute.

Is RPM for rotational or tangential speed?

RPM is used for rotational speed.

The unit needed to convert RPM into.

Radians per second (rad/s)

How does the size of rotational inertia affect a rotating object?

Bigger inertia = harder to start or stop spinning.

What two things does rotational inertia depend on?

Mass and distance from axis

What does torque cause?

Causes rotation.

Torque depends upon what

Force and lever arm length

2 ways to Increase torque

Apply more force or use a longer lever arm.

The unit for torque.

Newton-meter (Nm)

Directions of torque

Clockwise and counterclockwise.

How can we use torque to prove something is balanced?

If clockwise torque = counterclockwise torque, it’s balanced.

Where is the lever arm measured from and to?

Measured from the axis of rotation to where the force is applied.

Does increasing the lever arm make it easier or harder to rotate an object?

Increasing the lever arm makes it easier to rotate an object.

Does the force need to be perpendicular to the lever arm to cause torque?

Perpendicular

What is the center of mass/gravity

The point where an object’s mass is evenly balanced.

Where can the center of gravity be located

It can be inside or outside the object.

Name two things explained by Center of gravity

Balance and how objects fall.

Does the CG have to be in a place where the actual mass exists?

No

Explain the toppling Rule

If the Center of Gravity is outside the base, the object will tip over.

Is centripetal force a real or fake force?

A real force.

What is the direction of centripetal force

Toward the center of the circle.

 Is centrifugal force a real or fake force?

A fake force (it’s an effect of inertia).

Direction of centrifugal force

Outward from the center.

What are the Centrifugal force causes?

Inertia resisting change in direction.

Why do you feel as if you are being pushed outward during circular motion?

Your body wants to keep going straight due to inertia.

Provide examples of real-world applications of centripetal and centrifugal forces.

 Centripetal – roller coasters, turning cars
Centrifugal – spinning rides, washing machine spin cycle

How is simulated gravity created in space?

Created by spinning a space station, it pushes people outward like gravity.