Describe the construction and working of physical balance

Difficulty: Medium

Physical balance:

A physical balance is used in the laboratory to measure the mass of various objects by comparison.

Construction and working:

It consists of a beam resting at the Centre on a fulcrum.

The beam carries scale pans over the hooks on either side. An unknown mass is placed on the left pan. Find some suitable standard masses that cause the pointer to remain at zero on raising the beam.

### MINI EXERCISE

1. What is the function of balancing screws in a physical balance?

Ans: We use the balancing screws to remove the zero error of the physical balance. Balancing screws in a physical balance are used to bring the pointer to zero position.

### OR (Second answer)

There are two screws on the physical balance. One is on the left side and the other is on the right side of the physical balance. If the pointer is not in the middle of the scale, we move these screws forwards or backward to bring the pointer to the middle of the scale. This is done before we put any mass or weight in either of the pans.

In other words, we use the screws to remove the zero error of the physical balance.

2. On what pan do we place the object and why?

Ans: We Place the object into the left pane. In the case of physical balance, there the body is fixed and the weights have to be added in denominations. So only for convenience, we put the weights on the right pan after keeping the body on the left pan. I suppose a left-handed person weighs in a physical balance then no harm in placing the body in the right pan and putting the denominations of the weights on the left pan.