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Physics Test - 22

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Physics Test - 22
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  • Question 1
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    The force that binds the atmosphere around the Earth is the:

    Solution

    The force that binds the atmosphere around the Earth is the force of gravity.

  • Question 2
    1 / -0

    An ideal gas is heated at constant pressure so as to triple its volume. Find the increased temperature of the gas if initial temperature of gas is \(27^{\circ}\) C.

    Solution

    Pressure is constant \(P _{2}= P _{1}\)

    Volume is doubled \(V _{2}=3 V _{1}\)

    \(T _{1}=27^{\circ}\) C \(=273+27=300 K\), \(T _{2}=?\)

    Ideal gas equation,

    \(PV = nRT\), \(n =\frac{P V}{R T}\)

    During the whole process, no. of moles will not change.

    So, \(n_{1}=n_{2}\)

    \(\frac{P_{1} V_{1}}{R T_{1}}=\frac{P_{2} V_{2}}{R T_{2}}\)

    \(\frac{P_{1} V_{1}}{300 R}=\frac{\left(P_{1}\right)\left(3 V_{1}\right)}{R T_{2}}\)

    \(\frac{1}{300}=\frac{3}{T_{2}}\)

    \(T_{2}=900 K\)

  • Question 3
    1 / -0

    A point particle of mass \(0.1 \mathrm{~kg}\) is executing SHM of amplitude \(0.1 \mathrm{~m}\). When the particle passes through the mean position, its \(\mathrm{KE}\) is \(8 \times 10^{-3} J\). The equation of motion of this particle, if its initial phase of oscillation is \(45^{\circ}\).

    Solution

    Given:

    A point particle of mass \(0.1 \mathrm{~kg}\) is executing SHM of amplitude \(0.1 \mathrm{~m}\).

    \(\mathrm{KE}\) = \(8 \times 10^{-3} J\)

    Initial phase of oscillation = \(45^{\circ}=\frac{\pi}{4}\)

    We know that:

    \(\mathrm{KE}\) at mean position \(=\frac{1}{2} m \omega^{2} a^{2}\)

    According to the question:

    \(\frac{1}{2} m \omega^{2} a^{2}=8 \times 10^{-3}\).....(1)

    Put all the given values in (1).

    \(\omega=\left(\frac{2 \times 8 \times 10^{-3}}{m a^{2}}\right)^{\frac{1}{2}}\)

    \(=\left[\frac{2 \times 8 \times 10^{-3}}{0.1 \times(0.1)^{2}}\right]^{\frac{1 }{2}}\)

    \(=4\)

    Equation of SHM is,\(y=a \sin (\omega t+\theta)\)

    \(=0.1 \sin \left(4 t+\frac{\pi}{4}\right)\)

  • Question 4
    1 / -0

    Given the resistances of \(1 \Omega, 2 \Omega, 3 \Omega\), how will be combine them to get an equivalent resistance of:

    Solution

    The resistance of the given resistors is, \(\mathrm{R}_{1}=1 \Omega, \mathrm{R}_{2}=2 \Omega, \mathrm{R}_{3}=3 \Omega \),

    1. Equivalent resistance, \(\mathrm{R}=\frac{11}{3} \Omega\)

    Consider the following combination of the resistors.

    Equivalent resistance of the circuit is given by,

    \(R=\frac{2 \times 1}{2+1}+3=\frac{2}{3}+3=\frac{11}{3} \Omega\)

    2. Equivalent resistance, \(\mathrm{R}=\frac{11}{5} \Omega\)

    Consider the following combtnatlon of the resistors.

    Equivalent resistance of the circuit is given by,

    \(\mathrm{R}=\frac{2 \times 3}{2+3}+1=\frac{6}{5}+1=\frac{11}{5} \Omega\)

    3. Equivalent resistance, \(\mathrm{R}=6 \Omega\)

    Consider the series combination of the resistors, as shown in the given circuit. Equivalent resistance of the circuit is given by the sum.

    \(\mathrm{R}=1+2+3=6 \Omega\)

    4. Equivalent resistance, \(\mathrm{R}=\frac{6}{11} \Omega\)

    Consider the series combination of the resistors, as shown in the given circuit. Equivalent resistance of the circuit is given by,

    \(\mathrm{R}=\frac{1 \times 2 \times 3}{1 \times 2+2 \times 3+3 \times 1}=\frac{6}{11} \Omega\)

  • Question 5
    1 / -0

    Which of the following statement can define the Lenz law?

    Solution

    Lenz's law: It states that the direction of the induced current in the coil will be always in such a way that it opposes the change which produces the current.

  • Question 6
    1 / -0

    One requires \(11eV\) of energy to dissociate a carbon monoxide molecule into carbon and oxygen atoms. The minimum frequency of the appropriate electromagnetic radiation to achieve the dissociation lies in:

    Solution

    It is given, the energy required to dissociate a carbon monoxide molecule into catbon and oxygon atoms is \(E = 11 eV\)

    We know that, \(E=h f=6.62 \times 10^{-34} J - s\)

    \(f=\) frequency

    \(\Rightarrow 11 eV =h f\)

    \(f =\frac{11 \times 1.6 \times 10^{-19}}{6.62 \times 10^{-34}}=2.65 \times 10^{15} Hz\)

    Hence, the frequency required for the dissociation is 2.656×1015 Hz and it lies in the range of UV region. 

  • Question 7
    1 / -0

    What is the shortest wavelength present in the Paschen series of spectral lines?

    Solution

    Rydberg's formula is given as:

    \(\frac{h c} {\lambda}=21.76 \times 10^{-19}\left[\frac{1 }{\left(n_{1}\right)^{2}}-\frac{1 }{\left(n_{2}\right)^{2}}\right]\)

    Where,

    \(\mathrm{h}=\) Planck's constant \(=6.6 \times 10^{-34} \mathrm{Js}\)

    \(\mathrm{c}=\) Speed of light \(=3 \times 10^{8} \mathrm{~m} / \mathrm{s}\)

    \(\left(\mathrm{n}_{1}\right.\) and \(\mathrm{n}_{2}\) are integers)

    The shortest wavelength present in the Paschen series of the spectral lines is given for values,

    \(\mathrm{n}_{1}=3\)

    \(\mathrm{n}_{2}=\infty\)

    By putting the values, we get

    \(\frac{hc }{ \lambda}=21.76 \times 10^{-19}\left[\frac{1}{ (3)^{2}}-\frac{1 }{(\infty)^{2}}\right]\)

    \(\therefore \lambda=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8} \times 9} { 21.76 \times 10^{-19}}\)

    \(=8.189 \times 10^{-7} \mathrm{~m}\)

    \(=818.9 \mathrm{~nm}\)

  • Question 8
    1 / -0

    A uniform chain of length \(2 \mathrm{~m}\) is kept on a table such that a length of \(60 \mathrm{~cm}\) hangs freely from the edge of the table. The total mass of the chain is \(4 \mathrm{~kg}\). What is the work done in pulling the entire chain on the table ?

    Solution

    As we know if we pull the chain, each part of the chain will not cover same height, therefore will not contribute the same potential energy, so let's take mass of the chain \(L^{\prime}=\frac{L}{2 n}\)

    Now we can write

    \(W=\frac{m g L}{2 n^2}\)

    Given, 

    length \(2 \mathrm{~m}\)

    mass = \(4 \mathrm{~kg}\)

    After putting all the values and solving

    \(=\frac{4 \times 10 \times 2}{2 \times\left(\frac{10}{3}\right)^2}=3.6 \mathrm{~J}\)

  • Question 9
    1 / -0

    A block of mass \(2\) kg rests on a rough inclined plane making an angle of \(30^\circ\) with the horizontal. The coefficient of static friction between the block and the plane is \(0.7\). The frictional force on the block is:

    Solution

    Given,

    Mass \((m)=2\) kg

    Coefficient of limiting friction \((\mu)= 0.7\)

    Inclined plane making angle \((\theta)= 30^\circ\)

    As we know,

    The force applied on the body that is on the inclined plane is given as,

    \(F = mg \sin \theta\)

    \(\therefore F =2 \times 9.8 \times \sin 30^{\circ}\)

    \(=2 \times 9.8 \times \frac{1}{2}\)

    \(=9.8\) N

    The limiting friction force between the block and the inclined plane is given as,

    \(f =\mu mg \cos \theta\)

    \(\therefore f =0.7 \times 2 \times 9.8 \cos 30^{\circ}\)

    \(= 0.7 \times 2 \times 9.8 \times \frac{\sqrt{3}}{2}\)

    \(=11.88\) N

    Since the limiting friction force is greater than the force that tends to slide the body.

    Thus, the body will be at rest and the force of friction on the block is \(9.8\) N.

  • Question 10
    1 / -0

    A lady goes to a shop which is 2 km from her house. On reaching the shop she finds it locked and returns back home. Her final displacement would be:

    Solution

    Displacement is the distance between the initial and final position after the motion or journey of an object.

    Displacement is a vector quantity and can be obtained from the difference of position coordinates of the initial and final positions.

    The lady starts the journey from her home (initial point) and reaches back to her home (final point) upon seeing the shop closed. Here, the initial and final point at the end of the journey is the same. So, the displacement is zero.

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