DSSSB PGT Physics Mock Test - 2 - DSSSB TGT/PGT/PRT MCQ

• A physical quantity is a physical property of a phenomenon, body, or substance, that can be quantified by measurement.
• A physical quantity can be expressed as the combination of a magnitude expressed by a number – usually a real number – and a unit.
• All these given above can be expressed as explained so these are physical quantity.

Explanation:The sum of two or more vectors is called the resultant. The resultant of two vectors can be found using either the triangle method or the parallelogram method.

Explanation:A particle with a vertical and horizontal velocity travelling in a gravitational field will trace out a parabola.

Explanation:In order to take a safe turn, the cyclist has to bend a little from his vertical position. In this case, a component of the reaction provides the required centripetal force.If q is angle made by the cyclist with the vertical then

In actual practice, the value of q is slightly less because the force of friction also contributes towards the centripetal force.

Let mass of the block be m.

Frictional force in rest position F = mg sin 30⁰

[This is static frictional force and may be less than the limiting frictional force]

Using energy conservation,

Given,
Mass = 0.5 kg
At x = 0
vi = 3(0²) + 4 = 4
At x = 2
vf = 3(2)² + 4
= 16

For every large distance, P.E. = 0
Total energy = 2.6 + 0 = 2.6 eV
Finally, in the first excited state of H atom, total energy = -3.4 eV
Loss in total energy = 2.6 - (-3.4) = 6 eV
It is emitted as photon.

= 1.45 × 10⁹ MHz

Potential energy of a spring is proportional to the square of the difference of the springs length and its original length, hence whether it is compressed or stretched the potential the potential energy will eventually increase only.

On solving we get 3L/4
 

Hence v = v/4
 

Acceleration (a) = 9.8 m/s²

Weight of the body = 9.8 N

Since, Weight of the body = mg

⇒ Mass = Weight/g = 9.8/9.8 = 1 kg

We know that,

F = m × a

⇒ F = 1 kg × 9.8 m/s²

⇒ F = 9.8 Newton

The gravitational force of the earth acts on every object having mass. When a ball is thrown upwards the gravitational force of the earth acts against the velocity of the object and pulls the ball downwards, i.e, towards itself.

Thus, gravity pulls a ball back to earth.

The universal law of gravitation:

• Sir Isaac Newton put forward the universal law of gravitation in 1687 and used it to explain the observed motions of the planets and moons.
• The law states that every particle attracts every other particle in the universe with force directly proportional to the product of the masses and inversely proportional to the square of the distance between them.
  
• Formula, Gravitational force,  where, F is the gravitational force between bodies, m1, and m2 are the masses of the bodies, d is the distance between the centers of two bodies, and G is the universal gravitational constant.

• Here, universal gravitational constant, G = 6.67 × 10^-11 Nm/kg²

• The Universal Gravitational Law can explain almost anything, right from how an apple falls from a tree to why the moon revolves around the Earth.

Newton's third law of motion

• It states that for every action, there is an equal and opposite reaction.
• Action and reaction always act on two different bodies.

Explanation:

By Newton's Third Law and Newton's Law of Universal gravitation, the gravitational force the Earth exerts on the Moon is exactly the same as the force the Moon exerts on the Earth. 
F_(Earth) = F_(Moon)
Therefore, the moon attracts the earth with a gravitational force of 10²⁰N.

Concept:

Newton's law of gravitation: The force of attraction between any objects in the universe is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

• The force acts along the line joining the two bodies.
• The gravitational force is a central force that is It acts along the line joining the centers of two bodies.
• It is a conservative force. This means that the work done by the gravitational force in displacing a body from one point to another is only dependent on the initial and final positions of the body and is independent of the path followed.

• The moon revolves around the earth in a circular orbit (not perfectly circular). Sun exerts a gravitational force on both, the earth and moon. The major force acting on the moon is due to the gravitational force of attraction of the sun and earth and the moon is not always on the line joining the sun and earth. 
• Two forces acting on the moon have different lines of action or the forces are not central, so it's motion will not be strictly elliptical.

Hence, option (2) is the correct answer.

Concept:

Newton's law of gravitation: The force of attraction between any objects in the universe is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

• The force acts along the line joining the two bodies.
• The gravitational force is a central force that is It acts along the line joining the centers of two bodies.
• It is a conservative force. This means that the work done by the gravitational force in displacing a body from one point to another is only dependent on the initial and final positions of the body and is independent of the path followed.

Explanation:

• The gravitational force on mercury due to the sun is very large than that due to the earth.
• As observed from the earth, the sun appears to move around the earth in a circular orbit though, in reality, the earth moves around the sun due to gravitational force between them
• All planets move around the sun due to the huge gravitational force of the sun acting on them.
• Since the gravitational force on mercury due to the earth is smaller as compared to that on it due to the sun therefore it revolves around the sun and not around the earth.

Hence, option (3) is the correct answer.

Fluid Mechanics deals with the study of fluid at rest or in motion with or without the consideration of forces, Fluid Statics is the study of fluid at rest, Fluid Kinematics is the study of fluid in motion without consideration of forces and Fluid Dynamics is the study of fluid in motion considering the application forces.

The rate of loss of heat by a body is directly proportional to its excess temperature over that of the surroundings provided that this excess is small.

As change of state depends on both temperature and pressure, so, either method A or C can be used. We can understand this by ideal gas equation PV = nRT

It works on the principle that no machine is 100% efficient. For instance if taking an ideal machine into consideration, work can be completely converted to heat. Now if the conditions are reversed, all heat cannot be converted to equal amount of work until and unless backed up by an external force.

We know that PV=nRT also PM=dRT
So in the equation The value of R depends on P , V , n , T , d , M
except atomicity 
 so the ans is A

Electric force on a charge q placed in a region o electric field intensity is E and it is given by F = qE.
In this case, F = 100 N and q = 2 C.
So, E=F/q​=100N/2C​=50 N/C.
Hence, the value of field intensity will be 50 N/C.

Field intensity is proportional to the inverse of the square of the distance separating the point charges:

F = k*q1*q2/d^2

Since k, q1, and q2 are assumed to be constant, their product can be combined to form a single constant:

K = k*q1*q2, so

F = K/d^2 (and by algebraic manipulation we have K=F*d^2).

Therefore we know that

F(at d=4) = K/4^2, and

F(at d=2) = K/2^2.

Since K is a constant, we can equate K=F*d^2 for each case:

K=F(at d=4)*4^2 = F(at d=2)*2^2

so

F(at d=2) = (F(at d=4)*4^2)/2^2

F(at d=2) = 200N/C * (4^2)/(2^2) = 200N/C *16/4 = 800N/C.

Gauss law relates the electric flux density and the charge density. Thus it can be used to compute the radius of the Gaussian surface. Permittivity and permeability are constants for a particular material.

The voltage developed by the cells in parallel connection cannot be increased by increasing the number of cells present in the circuit. It is because they do not have the same circular path. In parallel connection the connection provides power based on one cell.
The voltage will remain the same.

Case 1 : Magnetic field at M due to PQ and QR is

Case 2 : When wire QS is joined.
H₂ = (Magnetic field at M due to PQ) + (magnetic field at M due to QR) + (Magnetic field at M due to QS)

NOTE : The magnetic field due to an infinitely long wire carrying current at a distance R from the end point is half that at a distance R from the middle point.

Let us consider a thickness dx of wire. Let it be at a distance x from the centre O.

Number of turns per unit length

∴ Number of turns in thickness dx =dx

Small amount of magnetic field is produced at O due to thickness dx of the wire.

On integrating, we get,

Explanation:As magnetic monopole does not exist. If we split the bar magnet into two pieces  each part will have its own north and south pole.