Laboratory experiment
ROTATIONAL EQULIBRIUM Objectives: -
(I) to test the validity of the condition for rotational equilibrium
(II) to use the condition of rotational equilibrium to find the mass of an unknown object
Theory: -
The torque τ of a force F with respect to appoint O is defined as a vector whose magnitude T is given by the product T=F.d, where d is the lever arm, namely the distance between the axis of the force and point O. the condition for the rotational equilibrium of a body is that the total torque Ttot around any point is Zero. When the reference point O and all the forces of interest lie on the same plane, the torque of each force attempts to rotate the body in a clockwise or counter-clock wise sense. In such case, the condition for rotational equilibrium simplifies to stating that the sum of the “clockwise” torques should be equal to the sum of the “counter-clockwise” torques. The SI unit of torque is 1N.m.

Procedure:-
For the purpose of the experiment the equipment like meter stick, clamps, wire hangers, support stand, weight set, and triple beam balance is used. Before the experiment the meter stick, three identical clamps, and three identical hangers are weighted and averages of clamps and hangers are taken. We conducted two experiment using the same machine.

I. TESTING THE CONDITION OF ROTATIONAL EQUILIBRIUM
After making the necessary adjustment, we attached a 0.10kg mass to a clamp and hanger. It was placed 30 cm to the position of the stick. The distance from the location of the mass and the center of the mass O of the stick is measured. Then we added 0.05kg mass to the other end of the stick, and the location was arranged to make the meter stick approximately horizontal. Later, the distance from the pivot O to the location of the 0.05 kg is measured. Using the given formula, we calculated the distance 2 and the percentage difference between the measured and the calculated distance.

II. DETERMINATION OF AN UNKNOWN MASS

After testing the condition of rotational equilibrium, all the masses are removed from the hangers. An unknown mass mc was hanged on the hanger that is at a distance d1 from the pivot point O. a known mass of 0.05 kg was hanged to the opposite side and the position was adjusted to make the meter stick approximately horizontal. Later, the distance from the center pivot point is measured to the known mass. The unknown mass was weighted and the mass was recorded. We used the formula to calculate the unknown mass and we found the percentage difference between calculated and weighted mass of the unknown mass object.

Result:- As for the result of our experiment, we found out that the meter stick was approximately horizontal with two different masses with