Answer:
The volume of the block is equal to the volume of water displaced by the block.
Explanation:
Volume refers to the amount of space occupied by a given object (in this case the block). When an object such as the block is immersed in water, it displaces its own volume of water. This volume of water displaced is equal to the volume of the block. Hence we can write;
Final Volume of water - Initial Volume of water= Water Displaced = Volume of the block
Recall that the density of a body is given by;
Density= mass/volume
If we obtain the volume of the block by measuring the volume of water displaced by the block, then we weigh the block using a weighing balance, we can obtain the density of the block easily from the relationship shown above.
(a) The force exerted by the electric field on the plastic sphere is equal to

where

is the charge of the sphere and E is the strength of the electric field. This force should balance the weight of the sphere:

where m is the mass of the sphere and g is the gravitational acceleration.
Since the two forces must be equal, we have:

and so we find the intensity of the electric field

(b) Now let's find the direction of the field. The electric force must balance the weight of the sphere, which is directed downward, so the electric force should be directed upward. Since the charge is negative, the force is opposite to the electric field direction, and so the direction of the electric field is downward.
Huh? The answer is A Shadow