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# Tag Archives: work

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## Sequence of Learning Physics

In what sequence should these chapters be prepared for my exams:-
units and dimensions,kinematics,laws of motion,work power and energy,motion of system of particles and rigid body dynamics,gravitation.

It is better to follow the same pattern as given in NCERT text book ## Homework from vectors

A man walks 10 km towards west and then 12 km (60 degree_ direction of North-East. find the resultant vectors, magnitude and direction. A man walks 10 km towards west and then 15 km towards south. Find the resultant vectors, magnitude and direction. Justify and comments either quantity scalar or vector. Weight Temperature Velocity Work Distance Speed […]

## Can light do some mechanical work?

“We know that sound can cause some mechanical work(eg:when we keep our hand in front of a large speaker,we feel something hitting the back of our hand), but why this doesn’t happen with light??” -Manishankar asks. ## Preparing for IIT JEE Physics

Yudhvir asks: “Hello Sir!!! I m in 11th!! I want to do less work & more benefit!! I don’t like to study at all!!…but i have decided to do only DC Pandey!! is it enough for IIT preparation???”

Whatever be the book you follow, understanding the basic concepts is all the most important. Make sure that you can solve all the solved and unsolved exercise in CBSE text book. These questions are originally set by a group of experts who are also among the question paper setters for IIT JEE. If you can solve the NCERT text book problems with ease, you have acquired the required standard. Then you may take up any book for solving additional problems.

If you have any doubt, feel free to ask here.

Best if luck!

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• iitjee ## Misconception on Work and energy conservation

It is said that when work is done energy is lost. But when a man runs in a circular path and reaches the starting point, then the work done is zero but energy is lost. (Divyam asked)
Answer: The work done here is not zero, work is done and energy is spent to overcome friction. Though he is reaching the same point, he is moving against a non conservative force, friction (where the work done in a closed path is not zero) ## Is law of conservation of energy violated here?

“When a body is moving with uniform speed on a rough surface under the application of a constant external force and an equal and opposite frictional force, the work done by both the forces should be equal. as a result, the net work done by both the forces should be zero. however, we find that heat energy is also evolved in this process.where does this extra energy come from?”

The work done is against friction only and if there is no friction, a force is not required to keep a body in uniform motion. The work done against friction appears as heat. ## Dimensional Analysis – A solved example

Deduce the dimensional formula for workdone,pressure and density. [posted by boineelo ]

workdone

We know that workdone = force x distance

Therefore [work done] =  [force] [distance]

but force = ma

[force]=[m][a]

[a]=[velocity]/[t]

[velocity]=[displacement]/[t]

So, putting all these together

[work done]=[m][distance][distance]/[time][time]

[work done]=ML2T-2

Similarly, you can work out the dimensional formula for pressure and density as

[pressure]=[force]/[area]=ML-1T-2

[density]=[mass]/[volume]=ML-3

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