DSSSB PGT Physics Mock Test - 3 - DSSSB TGT/PGT/PRT MCQ

The incorrect statement is:

d) Unit of surface tension is Newton metre.

The correct unit of surface tension is Newton per metre (N/m), not Newton metre.

Here's a breakdown:

• a) Unit of K.E. is Newton-metre: True, because kinetic energy is measured in joules, and 1 joule equals 1 Newton-metre.
• b) Unit of viscosity is poise: True, poise is indeed a unit of dynamic viscosity.
• c) Work and energy have the same dimensions: True, both work and energy have the same dimensions and are measured in joules.
• d) Unit of surface tension is Newton metre: Incorrect, it should be Newton per metre (N/m).

Second law of motion gives:

Explanation:Equal vectors are vectors that have the same magnitude and the same direction. Equal vectors may start at different positions.

When the man rides, he should put an umbrella in the opposite direction to which the drops are falling with respect to him.
Hence wrt man, the speed of rain drop is
at an angle of tan^-1 ⅓
Hence he would put umbrella to the direction of tan^-1 ⅓

Given,

m= 0.3 kg, x = 20cm and k = 15N/m

F= -kx    ..(i)
and F = ma    ..(ii)
∴   ma = -kx

In the frame of wedge, the force diagram of block is shown in figure. From free body diagram of wedge.

For block to remain stationary

ma cos α = mg sin α

or         a = g tan α

Concept:

Conservative force:

• Work done due to conservative force in a loop is always zero.
• Work done due to conservative force is only depending on the initial and final position.
• E.g. Gravity force, spring force, Electrostatic force, Magnetic force.

Non-conservative force:

• Work done due to non-conservative force on loop is not zero.
• Work done due to non-conservative force is depending on the path.
• E.g. Friction force, Viscous force.

Explanation:

• The frictional force is not a conservative force.
• Magnetic force, static electric force, and Gravitational force are the conservative forces.
• Work done by Gravitational force depends upon the initial position and final position of the object while it is falling from a height. 
• It doesn't matter it is falling through steps, frictionless inclined plane, or just through from height. 
• This is not the case with frictional force. The work done by a fictional force depends upon the path taken.
• So, the correct option is frictional force

The time when the kinetic energy and potential energy of the system become equal can be determined as follows:

The condition for equal kinetic and potential energy is given by:
Kinetic Energy (KE) = Potential Energy (PE)

⇒  A² = 2x²

The displacement X is given by: X = A sin(ωt)

Solving these equations, 

A² = 2x²

X = A sinωt

x = 8 sec

Momentum is conserved in all types of collision whether it is elastic or inelastic where as kinetic energy is lost in sound energy in the absence of external force in inelastic collision.

Force between two stationary mass is gravitational force which is conservative. between two charge is electrostatic. muscular force is non conservative because we did work it lost or appear in form of heat and we need to eat food to gain energy for work done.

The forces acting on the body are the force of gravity and the air friction. By work energy theorem, the total work done on the body is
W=1/2m(1.2√gH)2−0=0.72mgH
The work done by the force of gravity is mgH.
. Hence, the work done by the air friction is,
=0.72mgH-mgH
=00.28mgH.
 

To find the height above the Earth's surface where the gravitational acceleration is one-fourth of its value at the surface, we can use the formula for gravitational acceleration:

Thus, the height at which the gravitational acceleration is one-fourth of that at the Earth's surface is R_e. 

 Escape velocity does not depend on the angle of projection. Escape velocity will remain the same.
Hence, escape velocity is 11.2km/s .

Explanation:External force permanently distubed the equilibrium position of the interatomic ( or intermolecular ) forces between the particles of solid bodies.

∆ U = ∆ Q - ∆ W
In an adiabatic process ∆Q is zero, therefore
∆ U = - ∆ W

Heat extracted from source Q1= 700 cal
Heat rejected to the sink Q2= 500 cal
Temperature of source T1= 150 +273= 423K
Temperature of sink T2 to be found:
 Q2/Q1 = T2/T1
So,
T2 = (Q2/Q1) x T1
= (500 x 423)/700
= 302.02 K
= 29.02 degree C.
 

Let particle (1) is moving towards right and particle (2) is moving towards left art this instant, 1 = 0 

∴ Amplitude is 0.4 m and motion is SHM.

Capacitance of an isolated spherical conductor =4π€R , where €=permittivity of vacuum
C=2×10^-6F
C=4π€R
4×3.14×8.85×10^-12×R=2×10^-6
R=2×10^-6/4×3.14×8.85×10^-12
=1.8×10⁴ m

KEY CONCEPT : The current in RC circuit is given by I = I₀e^–t/RC

On comparing with y = mx + C

When R is changed to 2R then slope increases and current becomes less. New graph is Q.

The current in 2W resistor will be zero because it is not a part of any closed loop.

Let us consider an elemental length dl subtending an angle dθ at the centre of the circle. Let F_B be the magnetic force acting on this length. Then

F_B = BI (dl)  directed upwards as shown

= BI (Rdθ)              

Let T be the tension in the wire acting along both ends of the elemental length as shown. On resolving T, we find that the components. cancel out and
the components.  add up to balance FB.
At equilibrium  

The relative permeability of ferromagnetic materials is much larger than 1. Ferromagnetic substances are those, which when placed in a magnetic field are strongly magnetized in the direction of the magnetizing field, i.e., it is strongly attracted by a magnet.

Given    P=50W, V_rms​=220V,
by     P=V_rms^2​​/R
or      R=V_rms²/P​​= 220²/50=968Ω
The peak voltage of the source is,
E_rms=E₀/√2
=>E₀=Erms x √2=220√2=311.13V
Now, 
I_rms​=V_rms​​/R
=220/968​
=0.227A
Hence option B is correct.

P_av=(V₀i₀/2) cosθ
In ideal capacitor θ= -π2
Cosθ=Cosθ(-π/2)=0
Therefore
P_av=0

Resonance is a condition in LCR circuit where the inductive reactance ( XL) and capacitive reactance (Xc) is equal.
Impedance at resonance is equal to the Resistance of the resistor because the other two cancel themselves off according to the below formula -
Z2=R2+(XL²-Xc²)
As XL = Xc ,
Z = R
 

The Critical Angle
a light ray is in the more dense medium and approaching the less dense medium.
The angle of incidence for the light ray is greater than the so-called critical angle.
When the angle of incidence in water reaches a certain critical value, the refracted ray lies along the boundary, having an angle of refraction of 90-degrees. This angle of incidence is known as the critical angle; it is the largest angle of incidence for which refraction can still occur. For any angle of incidence greater than the critical angle, light will undergo total internal reflection.

The electromagnetic waves are produced by vibration of an electric charge. This creates a wave which is both as electric and magnetic components. This way oscillates in perpendicular planes with respect to each other and in a phase.This creates all electromagnetic waves begin with an oscillating charged particle which creates an oscillating electric and magnetic field.