Tag: physics

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Multiple choice physics nuclei nuclear force the nuclear force nuclear force and binding energy

A hydrogen atom having kinetic energy $E$ collides with a stationary hydrogen atom. Assume all motions are taking place along the line of motion of the moving hydrogen atom. For this situation, mark out the correct statement(s)

  1. For $E\ge20.4\space eV$ only, collision would be elastic
  2. For $E\ge20.4\space eV$ only, collision would be inelastic
  3. For $E = 2.4\space eV$, collision would be perfectly inelastic
  4. For $E = 18\space eV$, the $KE$ of initially moving hydrogen atom after collision is zero
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

K.E=2P.E
For electron in hydrogen to excite, a minimum of 10.2eV energy is required. Therefore, minimum 20.4eV K.E is required for inelastic collision otherwise, electron would not accept energy. And if E=20.4eV, collision would be perfectly inelastic.
If E is less than 20.4eV, collision is elastic and the two hydrogen atoms exchange velocities.
Therefore, B,D are the correct answers.

Multiple choice physics nuclei nuclear force the nuclear force nuclear force and binding energy

Regarding a nucleus, choose the correct options :

  1. Density of a nucleus is directly proportional to mass number A.
  2. Nucleus radius $ \propto {{A}^{1/3}}$

  3. Nuclear forces are dependent on the nature of nucleons.

  4. Nuclear forces are short range forces.
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

Density of nucleus is: $\rho=\dfrac{A}{\dfrac{4}{3}\pi R^3}$
The radius of a nucleus, $R=r _0A^{1/3},$ so density of nucleus is independent of A and $R\propto {^3\sqrt{A}}$
The nuclear force is a short-range force because the distance between the nucleon is less than $0.7$ fermi (then the force is repulsive) and if greater than $10.7$ fermi (the force is attractive).

Multiple choice standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

The ratio of the C.G.S unit of pressure to the S.I unit of pressure is 10.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
SI unit of pressure is $N/m^2$ and CGS unit of pressure is $dyne/cm^2$.
We know that  $1 \ N = 10^5 \ dyne$  and   $1 \ m  =10^0 \ cm$
ratio of CGS unit to SI unit  $\dfrac{1 \ dyne/cm^2}{N/m^2} = \dfrac{1 \ dyne/cm^2}{10^5 \ dyne/(100)^2 \ cm^2} = \dfrac{1}{10} $
Thus the given statement is false.
Multiple choice standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

Find the SI unit of the following derived quantities :

Pressure

  1. Pascal

  2. Newton

  3. Kg

  4. length
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given pressure $\displaystyle = \frac{Force}{Area}$
$\therefore$ MKS unit of pressure $\displaystyle = \frac{S.I.  unit \ of \   force}{S.I.  unit \ of \ area} = \frac{kg  m  s^{-2}}{m^2}$
$\displaystyle = \frac{kg.m}{m^2 . s^2} = \frac{kg}{m.s^2}$
$\therefore$ MKS unit of pressure $= kg m^{-1} s^{-2}$
SI unit of pressure is pascal.