Physics, Chemistry, Mathematics Forums

Is strain a physical quantity?I have read somewhere that all physical quantities have units.Please help me.

A stone is tied to to a string of length 'l' and is whirled in a vertical circle with the other end as the centre. At a certain instant of time, the stone is at lowest position and has speed 'u'. The magnitude of change in velocity as it reaches a position where the string is horizontal ( acc. due to gravity = g ) is?

The answer that I am finding out is u - sqrt(u^2-2gl) using COME but the answer that actually the book says is sqrt(2gl) using third equation of motion.

Can anyone please help me in knowing the correct answer?
Thank You!

Find the locus of a point P such that PA.PB=constant where A,B are two fixed points.

How does magnetic field work?

Water flows through a horizontal tube as in figure(in the attachment provided.)If the difference of heights of water columns in the vertical tubes is 2cm and the area of cross sections at A and B are 4 cm² and 2cm² respectively,find the rate of flow of water through any section.

Q1. The electronic transition in hydrogen atom which accompanied by maximum release of energy is.

Answer: n=2 to n=1. 

Pls Explain why?

Q2.For the hydrogen atom, the energy of electron is -13.58/n2 eV. The minimum quantity of energy which it can absorb in its ground state is

Answer: 10.19 eV,

Explain pls,,,

Can circular motion occur even if there is not centripetal force?

Please consider the following case:

Take your pen's cap and hold it in your hand.Initially it is at rest.Then start moving it in a circular path.I know that we cannot rotate it in a complete circular path.But let us consider that it is rotating in a circular path.Then where is the centripetal force?Who is the provider of the centripetal force?So I suggest that circular motion can occur even if there is no centripetal force.

Now a question based on these facts:

An electric line of force in the x-y plane given by the equation x²+y²=1 .A particle with unit positive charge,initially at rest at the point (1,0),in the xy plane will move along the line of force.True or False.

It is written in our textbooks that the charged particle moves along the lines of lectric force.So the particle has to move along the circle.In this case thetre is no centripetal force,even then it is moving in a circle.

So my doubt is can a particle have a circular motion without any centripetal force?Please explain it in detail.

In an experiment on photoelectric effect,light of wavelength 800nm(less than threshold wavelength) is incident on a cesium plate at the rate of 5.0 W. Thepotetial of the coollector plate is made sufficiently positive to the emitter so that the current reaches its saturation value.Assuming that on the average one of every 106 photon is able to eject an photoelectron.The photocurrent in the circuit if in the form 8x*10^-7A.Find x.

For complete coagulation of 200 ml of As₂S₃ solution,10 ml 1M Nacl is required.What is the coagulating value of NaCl?

(A)200         (B)100       (C)50             (D)25

^{if the transversal Y = m}r^{x ; r = 123 cut offs equal intercepts on the transversal x+y=1 then
1+m}1^{, 1+m}2 ^{, 1+m}3 ^{are in AP , GP or HP}