Tape Standardization
When measuring distances or conducting surveys, it is important to ensure that the measuring tape being used is accurate. The accuracy of a measuring tape can be affected by various factors, such as temperature, tension, and sag. To compensate for these factors, the tape is usually standardized to a specific tension, known as the standardization pull.

Standardization Pull
The standardization pull is the tension at which the tape is calibrated to give accurate measurements. In this case, the tape has been standardized at a pull of 100 N.

Load Applied
Now, let's say a load of 120 N is applied to the tape during a measurement.

Sag Correction
Sag is the downward deviation of the tape from a straight line due to its weight and the applied load. It causes the tape to hang in a curve rather than being taut. Sag can introduce errors in the measurement, as the distance measured may be longer than the actual distance due to the curved tape.

To correct for sag, a sag correction needs to be applied to the measured distance. This correction is based on the sag formula, which takes into account the tension, weight per unit length, and span length of the tape.

The sag correction is given by the formula:

S = (L^2 * W) / (8 * T)

Where:
S = Sag correction
L = Span length
W = Weight per unit length of the tape
T = Tension in the tape

In this case, the standardization pull (T) is 100 N, and the load applied is 120 N.

Calculating Sag Correction
To calculate the sag correction, we need to know the span length (L) and the weight per unit length (W) of the tape.

Assuming the span length is, for example, 10 meters and the weight per unit length is 0.1 N/m, we can substitute these values into the sag correction formula:

S = (10^2 * 0.1) / (8 * 100) = 0.125 meters

Therefore, the sag correction is 0.125 meters.

Conclusion
In summary, when a load of 120 N is applied to a tape that has been standardized at a pull of 100 N, the sag correction is 0.125 meters. This sag correction is necessary to account for the curved shape of the tape caused by its weight and the applied load, ensuring accurate measurements are obtained.