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Efficiency of Air conditioner

someone designed an air conditioner that takes 500J of thermal energy from a cold room and exhausts 500J of thermal energy into the outside air. The energy is conserved, so the system should work.  Is such a system feasible or are we optimistic about this new design. Why or why not?

Questions from Class XI Physics

1. two boats moving parallel to each other and nearby are pulled towards each other. name the scientific theorem involved in the above cases. state and prove the theorem.

2. what are beats?name the basic phenomenon due to which beats are produced.two sources of sound are producing waves of frequency v1 and v2 where ( v1-v2) is small. show mathematically that the beat frequency is (v1-v2).

3. a body is projected with a velocity ‘u’ at angle theta with the horizontal. derive the mathematical equation of the path followed by the body and hence find the expression for the horizontal range. how will the horizontal range change if the angle of projection is changed to (90- theta).

4. using expression for pressure exerted by a gas on the walls of container, deduce Avogadro’s law.

5. a monkey of mass 40kg climbs on a rope which can with stand a maximum tension of 600N. in which of the following cases will the rope break:

a) if the monkey climbs up with an acceleration of 6m/s2
b) if the monkey climbs down with an acceleration of 4m/s2
c) if the monkey climbs up with a uniform speed of 5m/s
( ignore mass of rope. take g= 10 m/s2)

6. what is the need of banking of tracks?

7. the absolute temperature of a gas is increased to four times. what will be the change in its root mean square speed?

8. find the expression for apparent frequency observed by a stationary observer when a sound emitting source is approaching towards the observer.

9. a body weighs 63N on the surface of earth. what is the gravitational force on it due to the earth at a height equal to half the radius of the earth.

10. show that the co- efficient of superficial expansion of a rectangular sheet of the solid is twice its co-efficient of linear expansion.

(Posted by Ritika)

Continuity of Magnetic Field Lines

I was taught in school that magnetic lines can not cross each other without breaking. Also i was taught that magnetic field lines are unidirectional traveling out of the north end of the magnetic field and connecting to the south magnetic pole. My question is, In the event of the lines being broken, would the broken or open north magnetic lines coming out of the north pole of the magnetic field( traveling at the speed of 186,000 miles per second, the speed of light) be able to connect with any other south magnetic poles they encounter even a second or more away.thank you, Ron G.

The curvature of earth and a metal pipe!

I’ve been wondering about the following issue for the past few days, let’s assume all terrain on earth is plain, we have infinite supply of straight pipe sections we can assemble into a very straight long pipe all over the equator, if we observe a small part of the pipe let’s say, 10 or 100 meters it would appear straight, but as a whole, would it continue to be so straight that it would form an increasing angle with the surface as the planet’s surface becomes curved? Or would the pipe become ring along the planet? and in this case, how could it become a ring if it’s all straight pieces of rigid metal pipe? because of the curvature of space due to gravity? or because long things tend to bend in proportion to how narrow or thick they are respect to the lenght?? English is not my mothertongue, I hope i made myself clear enought in depicting the esense of my question. Thank you.

Posted by Jesus Bitar

Why there is no magnetic field around a disconnected copper wire

Moving electrons produce magnetic field right? Electrons on earth are moving at an average of 27.83m/s due to earths rotation plus 30m/s due to earths revolution and may be more due to sun’s revolution and our galaxy’s revolution.
since there is no absolute motion, how can we tell if electrons are moving?
If the electrons are moving, anyway, why is there no magnetic field around a disconnected copper wire?

Why protons and electrons do not collapse and cancel?

According to Physics opposite charges always attract But in an atom the distance between nucleus and electrons are small then why electrons didnt combined with protons? protons and electrons have opposite charges.But why they didnt combined each other?

“Good question,, both sub-atomic particle have certain mass and energy,, we also know that it,, there is electrons revolved an nucleus and their corresponding energy level,, so that it don’t care their charges.. only arrange respect that energy,,,,

the minimum distance between nucleus and orbital electron have minimum energy, as well as large distance it as more energy.”

Majoring in physics?

Hi there, I have finally (at 22 and third year in college) decided what I want to major in–physics! I love it, so so so much! I especially want to be an astrophysicist. However, after hearing from a bunch of people, my professor included, astrophysicists don’t get paid much, and a lot of people want to do it. This really bummed me out, because that’s my true passion. However, I don’t want to major in it, spend 8 years in school, and then not find a job, or find a lower paying job. I have a daughter, and I don’t have room to take chances too much. I need to get stable for the both of us. I genuinely want a six figure salary, and I would love to be able to do research, my life goal is to make a major contribution to physics. However, I just don’t know what I can do with a physics degree that will get me paid a decent amount, while at the same time doing what I love. Any advice or suggestions?

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