Beam Balance

Materials required:

  •     Beam balance
  •     Box of weights
  •     A rectangular wooden block
  •     Pendulum bob


How does a beam balance work?

The leveling screws at the base are adjusted to make the pillar vertical. The beam is gently raised by turning the handle. If the pointer does not oscillate almost equally on either side of the central division of the scale, adjust the nuts suitably at the ends of the beam. 

Before determining the mass of the body one needs to calibrate the beam balance.

1.    To find the zero resting point (R0)

The balance is released and the pointer is allowed to oscillate freely. Three or five successive readings (three to the left and two to the right on the scale against which the pointer turns back during oscillations) are taken. These readings are called the turning points. The average turning point on the left and the average turning point on the right are separately calculated. The mean of these averages gives the zero resting point ( R0).

The method of calculation is given below.

Turning Points (T.P)
Left Right






Mean T.P  
Resting Point ,


2.    To find the sensibility of the balance (S)

For finding the sensibility, 10 mg weight is placed in the right pan and the resting point (R1) is determined as before. Then the sensibility S is calculated using the equation (2) explained in the 'Theory' tab. .

 Now let’s find out the mass of the body (M)   

The balance is arrested by turning the handle. The given body is placed in the left pan and it is counter balanced by a known mass (W) in the right pan. The resting point (R) is determined. The correct mass of the body can be calculated using the relation (1) explained in the the 'Theory' tab.

Note: The pointer of the beam balance always rests near the pan having less weight.

Simulation Procedure :

For Sensibility Checking

  • Release the knob.
  • Note three consecutive turning points (three at left and two at right).
  • Arrest the knob.
  • Click on open door.
  • Place 10 mg in the right pan of the balance.
  • Click on close door button.
  • Now release the knob.
  • Note three consecutive turning points(three  at left and two at right ).

After sensibility calculation,

  • Click on the open door button.
  • Click on 10 mg to remove it from the balance.
  • Select an object by a single click on bob/wooden block.
  • The object would counter balanced by selecting weights given on a single click.
  • Click on close door button.
  • Release the knob to note the turning points as before.
  • Repeat the steps for adding more weights or reduce weights to counter poise the weight in the left pan.
  • Click on the show result button to view the result.
  • A reset button is also provided to reset the entire the simulation.

Note: The pointer of the Beam balance always rest near the pan having lesser weight.


To find the weight of the body 

Loads in Pan Turning Points Mean Turning Points Resting Point
Left Right Left Right Left Right  
Nil Nil         R0=
Nil 10 mg         R1=



W=----g         R=



1.    Sensibility,   =................................................g / div
2.    Correct mass of the body,    = ............................g 


The mass of the body = ………...............……kg




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