Introduction:
When solving problems related to motion, it is important to understand which equation to use. The equations of motion are mathematical formulas that relate the motion of an object to its initial velocity, final velocity, acceleration, displacement, and time. By using these equations, we can calculate various quantities related to the motion of an object.

Understanding the problem:
To determine which equation to use, we need to carefully read and understand the problem. Identify the given information and what needs to be calculated. This will help us determine which equation(s) are relevant to the problem.

Equations of motion:
There are three main equations of motion that are commonly used to solve problems related to motion:

1. First equation of motion:
This equation relates the final velocity (v), initial velocity (u), acceleration (a), and time (t). It can be written as:
v = u + at

2. Second equation of motion:
This equation relates the displacement (s), initial velocity (u), final velocity (v), and time (t). It can be written as:
s = ut + 0.5at^2

3. Third equation of motion:
This equation relates the final velocity (v), initial velocity (u), acceleration (a), and displacement (s). It can be written as:
v^2 = u^2 + 2as

Choosing the appropriate equation:
Once we have identified the given information and what needs to be calculated, we can choose the appropriate equation(s) to solve the problem. Here are some scenarios where each equation can be used:

- If we know the initial velocity, acceleration, and time, we can use the first equation of motion to calculate the final velocity.
- If we know the initial velocity, acceleration, and time, we can use the second equation of motion to calculate the displacement.
- If we know the initial velocity, acceleration, and displacement, we can use the third equation of motion to calculate the final velocity.

Summary:
To determine which equation to use in a motion problem, carefully analyze the given information and what needs to be calculated. Choose the equation that relates the known quantities to the unknown quantity. By following this approach, we can effectively solve problems related to motion.