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## JEE 2014 IS NEAR … How to do the last minute preparation?

The Engineering aspirants of India are now towards the last round of preparation JEE 2014. The paper pen phase of the 2014 edition of the JEE-Mains is scheduled for April 6 and the online examinations will be conducted on April 9, 11, 12 and 19.

The duration of the examination is three hours and will test the candidates on physics, chemistry and mathematics.

Here we will have a brief discussion on how to go for the last round of preparation in Physics. The visitors are welcomed for participating in the discussion through the comment system. Just post your questions and queries as comments to this post.

In Physics the most important topic is MECHANICS, which includes kinematics, laws of motion, work power energy, rotational motion. Electrostatics, Current electricity, magnetic effects of current, electromagnetic induction and alternating current circuits along with the entire OPTICS are to be taken seriously. If you can make a complete thorough revision during the week ahead, you can certainly score very good marks in Physics.

After that if you get time, revise Bernoulli’s principle, Surface Tension, Elasticity with special attention to Young’s modulus.

These are the portions which need to be understood and applied rather than memorizing.

PLEASE MAKE IT A POINT TO SOLVE ALL THE EXERCISES FROM THE NCERT TEXT BOOK. (Including the additional exercises)

Do not neglect the chapter UNITS AND DIMENSIONS, THE ERROR ANALYSIS ETC.

Practice well, solve maximum number of problems and success will be yours. Have some doubts in Physics? Feel free to discuss them here. The questions can be posted here for discussion and hope to get a suitable answer.

## How is the surface tension direction found out?

Can you, sir, explain point 44 of the attached image on surface tension.

Here’s the link in case attachment doesn’t work:
http://www.sakshieducation.com/EAMCET/QR/Physics/Jr%20Phy/12Surface%20tension%20_198-208_.pdf

How is the surface tension direction found out?
{i know it tangential but in which direction along the tangent?}
Also why is surface tension for Solid-Air Surface considered when balancing forces on liquid?

Answer: Surface tension acts tangential to the surface of a liquid. If we imagine a line on the free surface of a liquid, the force of surface tension acts perpendicular to this line and tangential to the surface.

At a solid liquid interface the forces of cohesion and adhesion come to play.

In the diagram, T does not necessarily represent Surface Tension. Please remember that surface tension is the property of a liquid at surface.

Here T2 and T3 stand for the force at the point of contact along the solid surface. Further discussions are welcomed.

## Size of a soap bubble when charged

What will happen to the size of the soap bubble if the bubble is given charges ?

Answer: When a soap bubble is charged, its size increases.

Under normal condictions, a soap bubble is in equilibrium un der two opposing forces – the force of surface tension which tries to compress it and the force due to excess pressure which tries to expand it.

When charged, the force of repulsion among the like charges will try to expand the soap bubble further resulting in an increase in size of the bubble.

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