Kinds of Motion
Motion in a single straight-line direction is called this.
Translational motion
Even at constant speed, circular motion has acceleration because this is changing.
Direction (of velocity)
This measures how fast an object is spinning.
Angular velocity
Torque is how effectively a force can make an object do this.
Rotate
A simple machine is a device that changes the magnitude of this.
A force
Spin about an axis through the object itself is called this.
Rotation
The speed along the path of the circle is this kind of speed.
Tangential speed
On the slides, this direction of spin counts as positive.
Counterclockwise
This is the distance from the axis of rotation to the force.
Lever arm
Mechanical advantage is the ratio of output force to this.
Input force
Orbiting around an axis outside the object is called this.
Revolution
Centripetal acceleration and centripetal force both point toward this.
The center
A child on the rim of a merry-go-round has a larger one of these than a child near the hub.
Tangential speed
Pushing a door at the handle works better than pushing near the hinges because this is longer.
The lever arm
Efficiency compares these two values
Work output and work input
A bowling ball can slide without spinning, which shows rotation and this can be treated separately.
Translation
If the string breaks, the whirling ball next follows this kind of path.
A straight (tangent) path
This measures how hard it is to change an object’s rotation.
Moment of inertia
A force aimed straight at a door hinge produces little torque because of this about the force.
Its angle
A single fixed pulley is most useful for changing this about the applied force.
Its direction
The point a tumbling baton rotates around as it flies is this.
Center of mass
The outward “fling” you feel in a turning car is not a real force; it is this.
Inertia
Moving mass farther from the axis does this to moment of inertia.
Increases it
Torque gets larger if you increase the force or this.
Distance from the axis
An inclined plane can reduce the needed force because it increases this.
Distance