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# Tag Archives: United States

## units and measurement

THE LENGTH OF UNIFORM ROD IS 100.0CM AND RADIUS IS 1.00CM.IF LENGTH IS MEASURED WITH METER ROD HAVING LEAST COUNT 1MM AND RADIUS IS MEASURED WITH VERNIER CALIPERS HAVING LEAST COUNT 0.1MM,THE PERCENTAGE ERROR IN CALCULATED VOLUME OF CYLINDER IS?

## Participate in Google Sceince Fair 2016

As every year, Google Science Fair entries are now open. Students aged 13-18 can now participate by registering online at https://www.googlesciencefair.com/en/

Exciting prizes are awaiting the winners.

The Grand Prize winner will receive \$50,000 in scholarship funding.

The \$50,000 Google scholarship is intended to further the Grand Prize winner’s education. If a team wins the prize, the scholarship’s value will be divided equally among the teammates.

Act now and compete !

## Determine unknown frequency with the help of beats

Two frequencies sounded together produce 3 beats per second.If one of the frequencies is 400 vibrations per second,the other frequency will be?

There are two possibilities because the beat frequency is equal to the difference in frequencies of the two sounding bodies.

So, the unknown frequency can be either 397 Hz or 403 Hz. This can be verified by lagging/ loading one of the sounding bodies.

## Are the gases coming out when a refrigerator is opened vapours?

Are the gases coming out when a refrigerator is opened vapours? Then why is it called?

Asked by a 7th std student.

Air contains humidity (due to the presence of water vapour). Evaporation can take place at any temperature. However the rate of evaporation increases with increase in temperature..

The conversion of a liquid to gas can take place due to evaporation or boiling. but boiling is the phenomenon taking place at a higher but constant temperature.

Due to evaporation (and boiling) the air contains water vapour at room temperature.

When we open the fridge the water vapour condenses to tiny droplets of water and become visible (due to scattering of light).

(I feel that all the concepts might not have been cleared, please ask the questions which arise as comment to this post.)

## Does light experience friction?

Does light experience friction?

Asked rashmi (VIII B, KV AFS Bidar)

FRICTION  is defined as the force which opposes relative motion between two surfaces in contact.

If you mean friction in the normal sense as above (as discussed in class), then the answer is “NO“.

Light is a form of energy and not a particle. But it is true that light shows some particle behaviour also.

But, there is a slowing down when light interacts with matter. But, in a homogeneous medium, light has a constant speed. The speed of light is different in different medium.  If we go to the atomic or molecular picture of matter, then we can imagine that light is interacting with a molecule, during the time of interaction, the light can be assumed to have been absorbed by the particle and then it is re-radiated. the re-radiated light travels to the next atom and interacts/absorbed. this slows down the average speed of light, but is constant for a particular homogeneous medium.

The speed of light is maximum in vacuum where there is no matter for light to interact.

So, in between two atoms also, light travels with its branded 3L kmps speed.

Also refer:

1. http://phasing.org/2009/09/25/does-light-have-friction/

## Does Newton’s Third Law apply on throwing butter on a wall?

Newton’s third law of motion states that

“When we throw any object on anything, that thing also pushes back with the same force. But when we throw butter on the wall, it sticks on the wall. Why?”

Asked by Akshit and Koushal from Class VII A from Kendriya Vidyalaya Air Force Station Bidar, Karnataka

I feel that there is some misconception/misunderstanding here.

Newton’s Third law states that whenever two bodies interact each other, the force exerted by one body on the other is equal and opposite to the force exerted by the second body on first. These forces are simultaneous and are exerted on different bodies. tha is; the force exerted by the first body is acting on the second body and the force exerted by the second body is acted on the first body.

It doesn’t matter whether the body sticks to the other body or bounces back. We are concerned here with force and not with the motion.

When handful of butter (or clay) is thrown on to the wall, the ball of butter exerts some force on the wall. The wall exerts an equal force simultaneously. But the adhesive force between the wall and butter is more than the force acting on butter which tries to detach it. So it is not detached.

When a rubber ball thrown on the wall, the force exerted by the wall on the ball compresses it. Due to the elastic nature of the ball, it tries to bring the shape back to original and this makes it bounce back. The force exerted on the wall due to the bouncing ball is double that of a clay/butter ball of same mass hitting the the wall with same speed; because, the rubber ball requires the force to bounce back too.

http://www.phy-astr.gsu.edu/dhamala/Physics2211/Chapter9.pdf

## The Physics of Accidents

Accidents

Why are road accident at high speeds very much worse than accidents at low speeds?

As you might have studied, greater the speed, greater is the momentum. When an accidents occurs, the greater momentum involved can cause greater damage.

1. http://outreach.phas.ubc.ca/phys420/p420_96/danny/danweb.htm

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