If the tension in a string is doubled, then a natural frequency will (a) increase, (b) decrease by

(a) increase by times

Explanation:

Natural frequency of a wave in a string is given by:

where, L is the length of the string, T is the tension in the string and is the linear density of the string.

Considering the length and linear density of the string are constant, if the tension in a string is doubled, the natural frequency of the string would:

Thus, the natural frequency of the string would increase by   times.

pe = weightxheight = 2000x1000=2,000,000joules