In Newton’s laws of motion (or NLM), there are forces, frame of reference, and many other things are mentioned. In NLM, there are many points to keep in mind before applying Newton’s laws. But here we describe only five those steps that everyone should be follow before applying Newton’s laws.
As we know Newton gave three laws to describe the motion of any object known as Newton’s laws of motion. Basically Newton’s laws gives us the relationship between force and state of motion of an object.
State five steps to be followed to apply Newton’s law
These are the following steps that everyone should follow to apply Newton’s law.
Step 1:- Identify the forces acting on a body.
Step 2:- Identify the frame of reference.
Step 3:- After deciding frame of reference, draw a simple free body diagram (FBD).
Step 4 :- Mark and name the forces and tension in free body diagram (FBD).
Step 5:- After doing all steps. Apply Newton’s law in FBD.
Now, let’s understand all of the above steps one by one in detail with examples.
(1.) Identify the forces acting on a body
The first step is to identify the types of force acting on a body before applying Newton’s law. Because there may be many forces or may be only one force acting on a body. Some of the common forces that generally acts in all situations are describe below.
- Frictional forces:- If the body have contact to other body or to the ground then frictional force many exist. depending on the situations weather the frictional force is negligible or not.
- Weight:- Generally in all the situation weight (mg) exist. But the body should be on earth. weight is also a type of force that exerted by the ground towards it.
- Normal force:- If the body is in contact with ground or other material then normal force acted on it. Normal force always acted on upward direction balanced with weight of the body.
- Tension:- It is a type of force exerted on a body by string or rope. If the body is connected with rope or sting tension may exist.
(2.) Identify the frame of reference
After identifying the types of force acting on a body. the second step before applying Newton’s law is to identify the frame of reference weather it may be inertial or non-inertial frame of reference. Its totally depends on the situation or where the body is situated. deciding frame of reference is very important to apply Newton’s law because if we can’t do the whole question will change. So make sure to identify frame of reference of the body. There are two types of frame of reference.
- Inertial frame of reference:- In this frame the body is either on rest or in uniform motion. there is no external force applied.
- Non-inertial frame of reference:- In this frame the body is either accelerating or in non-uniform motion.
(3.) Draw a simple free body diagram (FBD)
After deciding the frame of reference, For simplicity in fig. draw a simple and clean free body diagram (FBD).
(4.) Mark and name the forces and tension in free body diagram (FBD)
After draw FBD mark Normal force on the upward direction of the body. as shown in above fig. mark weight in the downward direction, Frictional force where it acts, motion of the body etc. As mentioned in above fig.
(5.) Apply Newton’s law in FBD
After doing all the four steps. Now in step 5, its time to apply Newton’s law in free body diagram which we make for a given body. Applying newton’s law may depends on the many situation. As we discuss in earlier steps. It may be forces, Frame of reference, and other things.
Conclusion
From above discussion of all five steps, we conclude that for applying newton’s law on any question we must followed these five things. first we have to identify the forces acted on a body, second we should have identify in which frame of reference the body is situated, third we must draw FBD, forth we should mark all the important forces and tensions on FBD and at last in fifth steps apply newton’s law on a given body.