We know that V=E/Q Where V is the PD, E is the energy, and Q is the charge.
Substituting in the values gives V=48/4=12
Therefore the PD across the circuit is 12V
Answer:
The work done by gravity is 784 J.
Explanation:
Given:
Mass of the block is, 
Height to which it is raised is, 
Acceleration due to gravity is, 
Now, work done by gravity is equal to the product of force of gravity and the distance moved in the direction of gravity. So,

Force of gravity is given as the product of mass and acceleration due to gravity.
. Now,

Therefore, the work done by gravity is 784 J.
When we form a right triangle connecting the edge of the knife to the center of the circle and the center of the knife to the center of the circle, the radius of the circle becomes the hypotenuse. Using the trigonometric function,
sin 60° = opposite / hypotenuse = 4 / hypotenuse
The value of the hypotenuse is 4.62 inches. Then, the diameter is twice this value which is 9.24 inches.