**True.**

A watch is indeed necessary to measure the time period of a pendulum. In order to understand why, we need to first understand what a pendulum is and how its time period is calculated.

**What is a pendulum?**
A pendulum is a weight suspended from a fixed point that swings back and forth under the influence of gravity. It consists of a string or rod with a mass attached to the end. When the mass is displaced from its equilibrium position and released, it swings back and forth in a regular motion.

**What is the time period of a pendulum?**
The time period of a pendulum is the time it takes for the pendulum to complete one full swing. It is defined as the time required for the pendulum to move from one extreme position to the other extreme position and back again.

**Why do we need a watch to measure the time period?**
In order to measure the time period of a pendulum accurately, we need a device that can measure time precisely. A watch or a clock is a commonly used device for this purpose.

**Using a watch to measure the time period:**
1. Set up the pendulum: First, set up the pendulum by suspending it from a fixed point, such as a stand or a hook. Ensure that the pendulum is free to swing without any obstructions.

2. Start the watch: Begin timing by starting the watch at the same time you release the pendulum from its initial position. This will enable you to measure the time accurately.

3. Count the swings: As the pendulum swings back and forth, count the number of complete swings it makes. A complete swing is counted when the pendulum moves from one extreme position to the other extreme position and back again.

4. Stop the watch: Once you have counted a specific number of swings, stop the watch. Note the time displayed on the watch at this point.

5. Calculate the time period: To calculate the time period of the pendulum, divide the total time recorded on the watch by the number of swings counted. This will give you the average time for one swing or the time period of the pendulum.

By using a watch to measure the time period of a pendulum accurately, we can gather data and analyze the factors that affect the motion of the pendulum, such as the length of the string, the mass of the weight, and the gravitational force.

False because we will measure the time period of a pendulum with a formula.
The pendulum period formula, T, is fairly simple: T = (L / g)1/2