Answer:
The tension in the string is quadrupled i.e. increased by a factor of 4.
Explanation:
The tension in the string is the centripetal force. This force is given by

m is the mass, v is the velocity and r is the radius.
It follows that
, provided m and r are constant.
When v is doubled, the new force,
, is

Hence, the tension in the string is quadrupled.
An insulator which is also called a 'dielectric'.
Answer:
4.3 * 10 N
Explanation:
To calculate torque, we multiply the distance from the pivot by the perpendicular (the part of the force that acts at right angles to the displacement vector) component of the force to the displacement vector from the pivot.
torque = distance from pivot * perpendicular force
170 Nm= 0.4 m * F
F = 425 N = 4.3 * 10 N rounded off to two significant figures