Solving problems in Physics: KINEMATICS

CBSE Physics
CBSE Physics

Solving problems in Physics: KINEMATICS


How to solve problems in physics?

Solving problem in physics can be easy if you remember the advantage that most of the problems are based on our observation and common experiences in daily life and can be easily understood.

Read; visualise and if possible draw a diagram for the given situation.

Remember to note:

Where did the motion begin and where does it end?

What is the path followed by the body?

Are there any constraints in the problem?

Some of the useful tips and helpful strategies are listed below for particular types of problems.

Always keep your focus on comprehending methods; concepts and simple mathematical tools and not on specific types of problems the later may lead to rote learning ignoring the concepts of the subject.

Problem solving in Motion:

If the motion of the body is uniform; the only applicable equation in S = v.t.

However in some problems; the body may cover certain given distances S1; S2; S3 etc. with velocities V1; V2 and V3 etc. OR moved with velocities V1; V2; V3 etc. for times t1; t2; t3 …

In case of uniformly accelerated motion; record the given information and identify the unknown or the required quantity. Recall a relation between the given and the required quantity. This is a very important and may be most time consuming step.

It outlines the basic approach we are going to follow to approach the problem. With practice; this time can be drastically reduced. 

The more the practice; the lesser will be the time required which will help to instill the much needed confidence in solution to the problems. 

Calculate the required quantity and think about the removes/values obtained. The answer should be logical and should make sense.

Units are of immerse importance. Sometimes the units/dimensions may be a big help in getting to the correct option.

For projectile motion; analyse the horizontal and vertical motion separately.

The initial velocity, if given, you may resolve it into ux and uy. 

The horizontal velocity always remains unchanged throughout the motion and acceleration due to gravity (=9.8m/s²) acts vertically downwards. ay (or g) may be positive or negative defending on the sign conventions you choose. At the highest point in the trajectory vy becomes zero before the bodies begins its downwards motion.

Calculate the unknown quantities. You may need to combine X and Y components of vectors to get the magnitude and direction. The final answer should be logical.

Important: Remember that horizontal motion uniform and vertical motion is accelerated.

For vector addition problems; draw a diagram to scale on a set of axes. Resolve the vectors into components taking into consideration the sign of each component by appropriate quadrant. Add the X–components and Y–components separately with proper care of the sign of each component. If required; use Pythagoras theorem to get the magnitude of the resultant vector. The direction of the resultant can be calculated using trigonometry. For relative velocity problems, use the vector addition tips. Remember to use appropriate symbols/subscripts for relative velocity.

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Solving problems in Physics: KINEMATICS