Lab $6$ Force and Motion Basics LabObjective: What causes rotational motion? The determining concept for rotational motion is torque.

We will experiment with various situations to see how the concept of torque can be used to determine

the rotational motion.

Theory: The principle behind balance can be explained by torque. Torque is the critical concept for

rotational equilibrium. This can be explained by the balance experiment below:

In the explanation in this experiment, we use the mass of the object to express its weight, this will not

affect the result of our prediction since the same gravitational constant g is ignored for every object.

The unit of the length is also ignored since all the length measurements use the same unit. We choose to

call torques that produce a counterclockwise rotation positive, torques producing clockwise rotations

negative. The torque $(\backslash$tau $)$ is defined as the product of the force $($f $)$ and the level arm $($l$).$

$\backslash$tau $=$f l

With this convention, the torques produced by various mass are:

$$ the level arm of the $5$kg weight is $8,$ the torque it produced would be $5\backslash$times $8=40,$

$$ the level arm of the $10$kg weight is $2,$ the torque it produced would be $10\backslash$times $2=20.$

$$ The level arm of the $20$kg weight is $3,$ torque it produced would be $-20\backslash$times $3=60,$ we give it an

additional negative sign because it will produce a clockwise rotation if it acts on the system by

itself.

And as a result, the net torque is

$40+20+(60)=0$

And consequently the system is balanced or in rotational equilibrium since the net torque is zero.