Physics Test - 2

Correct Answer : prongs of the tuning fork are kept in a vertical plane

Photocurrent depends upon the rate of transmission of charges from one end to other. The number of charges released will depend only on number of electrons falling on the metal plates, given by intensity. Frequency increases only the kinetic energy of electrons. 

For photo-electron emission, 

(Incident energy \(E)=(\mathrm{K} . \mathrm{E} .)_{\max }+\)(Work function \(\phi\))

 or \(E=K.E_{max}+\phi\)

or \( E=5+6.2\)

or \(E=11.2 \mathrm{eV}\)

or \(E=11.2 \times\left(1.6 \times 10^{-19}\right) \mathrm{J}\)

As we know that:

\(\therefore \quad \frac{h c}{\lambda}=11.2 \times 1.6 \times 10^{-19}\)

or \(\lambda=\frac{\left(6.63 \times 10^{-34}\right) \times\left(3 \times 10^{8}\right)}{11.2 \times 1.6 \times 10^{-19}} \mathrm{~m}\)

or \(\lambda=1110 \times 10^{-10} \mathrm{~m}\)

or \(\lambda=1110\) Å

The incident radiation lies in the ultraviolet region.

In the transverse wave, the direction of disturbance and direction of propagation is always perpendicular.

Electromagnetic waves are transverse in nature. Electromagnetic waves are produced by an oscillating charged particle. Transverse wave generally forms in a medium that can sustain shearing strain.

The weight of the body can be calculated as,

W = mg

Acceleration of the body is g downward.

So a pseudo force will act in an upward direction which cancels the weight of the body.

Therefore the weight of the body in free fall is zero.

Hence the correct option is (A).

The displacement equation is given as:

 \( \mathrm{y}=4 \cos ^{2}\left(\frac{\mathrm{t}}{2}\right) \sin (1000 \mathrm{t})\).....(1)

Using \(2 \cos ^{2} \theta=1+\cos 2 \theta\) in equation (1),

\(\mathrm{y}=2[1+\operatorname{cost}] \sin (1000 \mathrm{t})\)

\(\therefore \mathrm{y}=2 \sin (1000 \mathrm{t})+2 \sin (1000 \mathrm{t})\cos t\) ....(2)

Using \(2 \sin A \cos B=\sin (A+B)+\sin (A-B)\) in equation \((2)\)

\(\mathrm{y}=2 \sin (1000 \mathrm{t})+\sin (1000 \mathrm{t}+\mathrm{t})+\sin (1000 \mathrm{t}-\mathrm{t})\)

\(\Rightarrow \mathrm{y}=2 \sin (1000 \mathrm{t})+\sin (1001 \mathrm{t})+\sin (999 \mathrm{t})\)

Thus 3 harmonic oscillations superimpose on each other to give the resultant motion \(\mathrm{y}\).

Using perpendicular axis theorem: 

2I_AC = I₀, where I₀ is the moment of inertia about an axis perpendicular to the plane of the lamina and passing through O. 

Both diagonals are perpendicular to each other.

Further, 2I_EF = Io

Two medians (lines dividing the sides of the square equally) are also perpendicular to each other, also perpendicular to the axis passing through the centre and perpendicular to the plane of lamina. 

The rate of change of angular velocity is defined as angular acceleration. If particle has angular velocity ω1 at time

t1, and angular velocity ω2 at time t2 , then

Angular acceleration α = ω2 – ω1 / t2 – t1

Hence, the correct option is ( D ).

A bird sitting on a high tension electric wire does not get electrocuted, because their feet are not good conductors of electricity.

Electricity flows along the path of least resistance. Birds don’t get shocked when they sit on electrical wires because they are not good conductors of electricity. Their cells and tissues do not offer electrons an easier route than the copper wire they’re already traveling along.

Escape velocity:

It is the minimum velocity with which a body should be projected from the surface of the planet so that the body reaches infinity.

It is given as,

\(\Rightarrow v_{e}=\sqrt{\frac{2 G M}{R}}\)

Where \(v_{e}=\) escape velocity, \(G=\) gravitational acceleration, \(M=\) mass of the planet and, \(R=\) radius of the planet

In the given expression of escape velocity, there is no term associated with the mass of the particle.

So, escape velocity is independent of the mass of the object. We can say that it does not depend upon mass or depend upon \(\mathrm{m}^{0}\) which is equal to one.