Question

Describe:
(a) How the diameter of a table tennis ball can be measured and
(b) How the radius of a thin wire can be measured.

Answer 1

The question in which it describes about the instrument which we need to use to find the given as

The diameter of a table tennis ball and
The radius of a thin wire.
So, in a solution part we tend to explain the part of the instrument and what is the procedure to handle that instrument to measure the given details.

Complete answer:
(a) The diameter of a table tennis ball
A Vernier Caliper can be used to calculate the diameter of a tennis ball.

A Vernier caliper can be used to calculate the diameter of a tennis ball. Place the ball between the jaws of your Vernier caliper. In the main scale, read the mark just before the Vernier scale's zero mark. Then, to convert to centimeters, look for the coinciding mark in the Vernier scale to the main scale and multiply it by $0.01$. Finally, apply the reading from your Vernier scale to the main scale reading.

(b) The radius of a thin wire can be measured.
A Screw Gauge can be used to calculate the radius of a thin wire.

A screw gauge is a high-precision tool. It has a precision of $0.001cm$ and is used to measure the radius of circular objects, often wires. It is made up of a hollow cylinder attached to a U frame. The hollow cylinder is connected to a ratchet for fine adjustment. The U frame is made up of a stud on one end and a screw on the other. This screw can be rotated within the nut by rotating the hollow cylinder known as the thimble, which is fitted in the U frame. This is referred to as the key scale. The thimble or hollow cylinder is divided into $50$ or $100$ equal bits. The circular scale is what it's called.

Note:
1. We use the meter scale to measure distances in our everyday lives. They're calibrated in centimeters and millimeters.
2. The least count is the shortest length that can be measured on a meter scale. The least count of a scale is usually $1$.
3. We may use this scale to calculate the length of items to within mm precision. However, this scale is inadequate for determining the size of small spherical specimens. As a result, a Vernier caliper and a screw gauge are employed.