Physics, Chemistry, Mathematics Forums

Somebody, clear my earlier doubt.

Can anyone provide me the proof and explanatin of the moment of inertia of "I" sections, like in the railway tracks being high?

consider two wires infinitely long   one placed along the x axis and the other along the y axis ata dist a above the x axis. i hope u can picturise it well because its very essental.

the horizontal one carries a curent in the +ve x dir. and the vertical one carries current in the +ve y dir.

now the vertical wire exp. a force to the right (due to other wire)  but the vertical one will not experience any force.

isnt newtons third law violated???

A coin is placed on a horizontal platform which undergoes vertical simple harmonic motion of angular frequency w. The amplitude of oscillation is gradually increased. The coin will leave the contact with the platform for the first time

(a) at the highest position of the platform.
(b) at the mean position of the platform.
(c) for an amplitude of g/w².
(d) for an amplitude of g²/w².

The reaction at eqbm. of an ester with hydroxyl ions is as follows:

CH₃COOCH₃ + OH^- <----> CH₃COOH + CH₃OH

The rate constant for this rxn. is K litre/mol/sec. and the conc. of ester is C₁ mol/litre while that of the OH^- ions is C₂ mole/litre.

Then,
a) rate =  KC₁²
b) rate = KC₁C₂
C) rate = KC₂²
d) Data insufficient

I have a doubt in a) and b). I think it should be a) but some of my friends are saying it should be b).
Plz. tell me the correct answer

This problem is given in the NCERT.
It goes as this:
Analysis shows that nickel oxide has formula Ni_0.98O₁₀₀. What fractions of the nickel exist as Ni⁺² and Ni⁺³ ions?
I am not getting accurate ans.
Plz. try it.

ANS. Ni⁺² = 96% , Ni⁺³ = 4%

Even after seeing a few books, I am unable to understand the basic difference between Centre of Mass & Centre of Gravity.

Please explain this & also tell how we can say that centre of mass of a body can lie outside the body?

I had a doubt in the following question of COORDINATE GEOMETRY.

The graph of the function

f(x) = cos x .cos (x+2) – cos²(x+1) is

(a)         a straight line passing through (0,0)

(b)        a straight line passing through (0,-sin²1) with slope 2.

(c)         a parabola with vertex (1,- sin²1)

(d)        a straight line passing through the point

       (pie/2, - sin²1) and parallel to the x-axis.

Please ans. it.

The ans. to this question is option (d) but explanation is required.

 

 

 

 

Find the electric potential at the apex of a cone whose curved surface (only) has surface charge density sigma. Slant height of cone is l and semi-vertical angle is theta.