Answer:
the tension in the string an instant before it broke = 34 N
Step-by-step explanation:
Given that :
mass of the ball m = 300 g = 0.300 kg
length of the string r = 70 cm = 0.7 m
At highest point, law of conservation of energy can be expressed as :


The tension in the string is:

Thus, the tension in the string an instant before it broke = 34 N