A semi-infinite solid is

A. a solid with a very high conductivity.
B. a useful with approximation for heat transfer calcualtions at or near the exposed surface of a solid at very short time spans or for very thickness mediums.
C. impossible to heat up or cool down.
D. infinitely extended in all directions

D. infinitely extended in all directions

Explanation:

A semi infinite solid is infinitely extended in every direction. It has a single surface and can extend when heat is applied.

The body of a semi infinite solid is idealised, that is, when there is heat present, it expands in all directions to infinity. It can be used for a thick wall because its shape can be changed when subjected to different levels of heat near its surface.

It is also expands as heat is applied because its thickness is negligible.

This idealized body is used for earth, thick wall, steel piece of any shaped quenched rapidly etc indetermining variation of temperature near its surface & other surface being too far to have any impact on the region in short period of time since heat doesn’t have sufficient time to penetrate deep into body thus thickness can be neglected

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.