Answer:
Part a)

Part b)

Explanation:
Since the ball and rod is an isolated system and there is no external force on it so by momentum conservation we will have

here we also use angular momentum conservation
so we have

also we know that the collision is elastic collision so we have

so we have

also we know

also we know

so we have


now we have


Part b)
Now we know that speed of the ball after collision is given as

so it is given as

Answer:
Please refer to the figure.
Explanation:
The crucial point here is to calculate the enclosed current. If the current I is flowing through the whole cross-sectional area of the wire, the current density is

The current density is constant for different parts of the wire. This idea is similar to that of the density of a glass of water is equal to the density of a whole bucket of water.
So,

This enclosed current is now to be used in Ampere’s Law.

Here,
represents the circular path of radius r. So we can replace the integral with the circumference of the path,
.
As a result, the magnetic field is

Answer:
Microwave towers are telecommunications towers that use microwaves to transmit telephone and television signals to other microwave towers.
Explanation:
This technology replaced existing transmission wires, but it is almost entirely obsolete as of 2015 due to the advent of fiber optics and other modern methods of telecommunication.