Download Turning Effect Pre-Lab (print version)

Below is a box at rest on the floor with some friction.
What would I have to do to get it to move at constant velocity?
Where FA  F fk

F fk

FA
Below is a box at rest on the floor with some friction.
What would I have to do to get it to move at constant velocity?
Where FA  F fk

F fk

FA
What happens if we put a force on a rigid object that can rotate about a fixed axis?
The force provides what we will call for now a “turning effect.”
Is the size of the force the only thing responsible for the turning effect?
Is the size of the force the only thing responsible for the turning effect?
Is the size of the force the only thing responsible for the turning effect?
Not only the force is responsible for the turning effect, but also where the force is applied
with respect to the axis of rotation.
Axis of Rotation
Look at the position of the door handle.
Why is it typically as far away as
possible from the axis of rotation?
The amount of “turning effect”
appears to depend on both the
magnitude of the force and where
that force is applied.
Line of action – line along which the force acts
Lever armr  – the perpendicular
distance between the axis of
rotation and the line of action of the
force (Moment arm)

F2  m2 g
r2

F2  m2 g
r1

F1  m1g
What combination of force and lever arm put the object in balance?
Purpose: To create a mathematical model that represents the “turning effect” as some
combination of the force and the lever arm.
r2
Do not forget, the
mass hangers also
have a mass
(50. g = 0.050 kg)
that must be
included in the total
mass.

F2  m2 g
r1

F1  m1g
Clockwise
Turning Effect
Counterclockwise
Turning Effect
Balanced
(equal in magnitude)