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JEE Main Mock Test - 3 - JEE MCQ


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30 Questions MCQ Test - JEE Main Mock Test - 3

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JEE Main Mock Test - 3 - Question 1

A capacitor C1 = 1.0 μF is charged up to a voltage V = 60 V by connecting it to battery B through switch (1). Now, C1 is disconnected from battery and connected to a circuit consisting of two uncharged capacitors, C2 = 3.0 μF and C3 = 6.0 μ F through switch (2), as shown in the figure. The sum of final charges on C2 and C3 is:

Detailed Solution for JEE Main Mock Test - 3 - Question 1


 

 Q = 40μC

JEE Main Mock Test - 3 - Question 2

The length, breadth and thickness of a rectangular sheet of metal are 4.234 m, 1.005 m, and 2.01 cm respectively. Give the volume of the sheet to correct significant figures.

Detailed Solution for JEE Main Mock Test - 3 - Question 2

Length , l = 4,234 m
Breadth, b = 1.005 m
Thickness , t = 2.01 x 10-2 m
Volume = l x b x t
⇒ V = 4.234 x 1.005 x 0.0201 = 0.0855289 = 0.0855 m3 (significant figure = 3)

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JEE Main Mock Test - 3 - Question 3

Population of a town is reported as 157,900 . Which of the following statements correct?

Detailed Solution for JEE Main Mock Test - 3 - Question 3

157900  implies that the population is believed to be within the range of about 157850 to about 157950.

In other words, the population is 157900 ± 50. The “plus-or-minus 50” appended to this number means that we consider the absolute uncertainty of the population measurement to be 50 – (–50) = 100.

We can also say that the relative uncertainty is 100/157900, which we can also express as 1 part in 1579, or 1/1579 = 0.000633, or about 0.06 percent.

JEE Main Mock Test - 3 - Question 4

The product of energy and time is called action. The dimensional formula for action is same as that for

Detailed Solution for JEE Main Mock Test - 3 - Question 4

Both are different from each other.
Energy × Time=(M1L2T−2)×(T1)=M1L2T−1
Force × Velocity=(M1L1T−2)×(L1T−1)=M1L2T−3
Impulse × distance=(M1L1T−1)×(L1)=M1L2T−1
Power=M1L2T−3
Angular Energy=M1L1T−2

JEE Main Mock Test - 3 - Question 5

 The Van der Waal equation for 1 mole of a real gas is

where P is the pressure, V is the volume, T is the absolute temperature, R is the molar gas constant and a, b are Van dar Waal constants. The dimensions of a are the same as those of

Detailed Solution for JEE Main Mock Test - 3 - Question 5

The answer is PV2
Solution,
As we know the Vander Waals equation is {P+(a/V2)} (V−b) =RT
Then,
The dimension of a is,
(a/V2) = (P)
Or, a=PV2

JEE Main Mock Test - 3 - Question 6

Force F is given in terms of time t and distance x by

F = A sin C t + B cos D x

Then the dimensions of  and  are given by

Detailed Solution for JEE Main Mock Test - 3 - Question 6

Dimension of [A]=[MLT-2]
Dimension of [B]=[MLT-2]
 
 [A]/[B]= [ M0L0T0]
CT=1
Dimension of  [C]=1/[T]=[T-1]
DL=1
Dimension of  [D]=1/[L]=[L-1]
[C][D] =[T-1]/[L-1]
=LT-1
 
A/B=Force/Force=[M0L0T0]
Ct=∠⇒C=Angle/Time=1/T=T-1
Dx=∠⇒D=Angle/Distance=1/L=L-1
∴C/D=T-1L-1 =[M0 LT-1 ]

JEE Main Mock Test - 3 - Question 7

If force (F) is given by F = Pt_1 + Qt, where t is time. The unit of P is same as that of

Detailed Solution for JEE Main Mock Test - 3 - Question 7

According to the principle of homogeneity of dimension, an equation is dimensionally correct when each term has same dimension on both sides of the equation. 

Since left side has dimension of force so the term Pt−1 will have also dimension of force. 

Thus, [P][T−1]=[F]=[MLT−2]

or [P]=[MLT−1]

We know that the dimension of momentum is [p]=[MLT−1]

JEE Main Mock Test - 3 - Question 8

When a wave traverses a medium, the displacement of a particle located at x at time t is given by y = a sin (bt - cx) where a, b and c are constants of the wave. The dimensions of b/c are the same as those of

Detailed Solution for JEE Main Mock Test - 3 - Question 8

Argument of sin is dimensionless and using principle of dimensional homogeneity, we get
∣bt∣=∣cx∣=[M0L0T0]
Thus, ∣b∣=T−1 and ∣c∣=[L−1]
Thus, dimensions of b/c are [LT−1], which is the same as the velocity of wave.

JEE Main Mock Test - 3 - Question 9

Which of the following sets cannot enter into the list of fundamental quantities in any system of units ?

Detailed Solution for JEE Main Mock Test - 3 - Question 9

We define length and time separately as it is not possible to define velocity without using these quantities. This means that one fundamental quantity depends on the other. So, these quantities cannot be listed as fundamental quantities in any system of units.

JEE Main Mock Test - 3 - Question 10

Which of the following is not the unit of time

Detailed Solution for JEE Main Mock Test - 3 - Question 10

Parallactic second is the unit of distance because parallactic second is an abbreviation of parsec. Parsec = Parsec is the Unit for larger distances.It is the distance at which a star would make parallax of one Second of arc.

JEE Main Mock Test - 3 - Question 11

What is the physical quantity whose dimensions are M L2 T-2 ?

Detailed Solution for JEE Main Mock Test - 3 - Question 11

Dimension of KE is ML2T-2
That of pressure is ML-2T-2
That of momentum is ML/T 
That of power is ML2T-3

JEE Main Mock Test - 3 - Question 12

Which pair of following quantities has dimensions different from each other

Detailed Solution for JEE Main Mock Test - 3 - Question 12

Moment of inertia =1/2​×mass×(Radius of gyration)2=[M1L2T0]
Moment of force = torque =N.m=[M1L2T−2]
Both are different from each other.

JEE Main Mock Test - 3 - Question 13

Measurement of a physical quantity is essentially the:

Detailed Solution for JEE Main Mock Test - 3 - Question 13

The Measurement of a given quantity is essentially an act or result of comparison between a quantity whose magnitude (amount) is unknown, with a similar quantity whose magnitude (amount) is known, the latter quantity being called a Standard.

JEE Main Mock Test - 3 - Question 14

A solid ball of radius R has a charge density ρ given by  for 0 ≤ r ≤  R. The electric field outside the ball is:

Detailed Solution for JEE Main Mock Test - 3 - Question 14

JEE Main Mock Test - 3 - Question 15

A heating element has a resistance of 100 Ω at room temperature. When it is connected to a supply of 220 V, a steady current of 2 A passes in it and temperature is 500°C more than room temperature. What is the temperature coefficient of resistance of the heating element?

Detailed Solution for JEE Main Mock Test - 3 - Question 15

Resistance after temperature increases by 500°C = 220/2 = 110 Ω
The variation of the resistance with temperature is given by:
R2 = R1(1 + α(T2 - T1))
110 = 100(1 + α × 500)

JEE Main Mock Test - 3 - Question 16

An observer is moving with half the speed of light towards a stationary microwave source emitting waves at frequency 10 GHz. What is the frequency of the microwave measured by the observer?

(Speed of light = 3 × 108 ms–1)

Detailed Solution for JEE Main Mock Test - 3 - Question 16

Doppler effect in light (speed of observer is not very small compared to the speed of light)

JEE Main Mock Test - 3 - Question 17

An external pressure P is applied on a cube at 0°C so that it is equally compressed from all sides. K is the bulk modulus of the material of the cube and α is its coefficient of linear expansion. Suppose we want to bring the cube to its original size by heating. The temperature should be raised by:

Detailed Solution for JEE Main Mock Test - 3 - Question 17

Due to thermal expansion,
Change in the volume is:

Due to external pressure, volumetric strain,

From 1 and 2, we have

Hence, change in temperature is given by:

JEE Main Mock Test - 3 - Question 18

Activities of three radioactive substances A, B and C are represented by the curves A, B and C, in the figure. Then their half-lives T1/2 (A) : T1/2  (B) : T1/2 (C) are in the ratio

Detailed Solution for JEE Main Mock Test - 3 - Question 18

Let's consider the equation for radioactive decay.

Based on the data given in the figure,

JEE Main Mock Test - 3 - Question 19

The ratio of mass densities of nuclei of 40Ca and 16O is close to

Detailed Solution for JEE Main Mock Test - 3 - Question 19

JEE Main Mock Test - 3 - Question 20

The graph which depicts the results of Rutherford gold foil experiment with α-particles is:

θ: Scattering angle
Y: Number of scattered α-particles detected
(Plots are schematic and not to scale)

Detailed Solution for JEE Main Mock Test - 3 - Question 20

*Answer can only contain numeric values
JEE Main Mock Test - 3 - Question 21

A hydrogen atom, initially in the ground state is excited by absorbing a photon of wavelength 980Å. The radius of the atom in the excited state, will be _____a0.
(hc = 12500 eV - Å)


Detailed Solution for JEE Main Mock Test - 3 - Question 21

Energy of photon = 12500/980 = 12.75 eV

∴ Electron will excite to n = 4

Since 'R' ∝ n2

∴ Radius of atom will be 16a0.

*Answer can only contain numeric values
JEE Main Mock Test - 3 - Question 22

A rigid diatomic ideal gas undergoes an adiabatic process at room temperature. The relation between temperature and volume of this process is TVk/5 = constant, then value of k is ______.


Detailed Solution for JEE Main Mock Test - 3 - Question 22

For adiabatic process : TVγ-1 = constant

For diatomic process : γ-1 = 7/5 - 1

∴ x = 2/5

*Answer can only contain numeric values
JEE Main Mock Test - 3 - Question 23

The gas mixture constists of 3 moles of oxygen and 5 moles of argon at temperature T. Considering only translational and rotational modes, the total inernal energy of the system is _______RT.


Detailed Solution for JEE Main Mock Test - 3 - Question 23

*Answer can only contain numeric values
JEE Main Mock Test - 3 - Question 24

A refrigerator is to maintain eatables kept inside at 9oC. If room temperature is 36oC, calculate the coefficient of performance.


Detailed Solution for JEE Main Mock Test - 3 - Question 24

Here, the temperature inside the refrigerator can be provided as, T1 = 9oC = 282 K
Room temperature is given as, T2 = 36oC = 309 K
Coefficient of performance can be given by the relation, COP = T1/(T2 - T1)

JEE Main Mock Test - 3 - Question 25

is equal to

Detailed Solution for JEE Main Mock Test - 3 - Question 25

JEE Main Mock Test - 3 - Question 26

Let ,Q,R and S be four points on the ellipse 9x2 + 4y2 = 36. Let PQ and RS be mutually perpendicular and pass through the origin. If , where p and q are coprime, then p + q is equal to :

Detailed Solution for JEE Main Mock Test - 3 - Question 26

Given, points P and Q are on the ellipse defined by 9x2 + 4y= 36 which simplifies to . This is the standard form of the equation of an ellipse centered at the origin, with semi-major axis a = 3 along the y-axis and semi-minor axis b = 2 along the x-axis.
OP is the distance from origin O to point P, which is given by :

1. Let's represent the given point  in polar coordinates. We can write 

Simplifying this, we obtain :

2. Similarly, if we represent the point R as ,   (the negative sign is due to the fact that line RS is perpendicular to line PQ. Since they are perpendicular, the angle between them is 90 degrees or π/2  radians. In terms of sin and 
it too should satisfy the equation of the ellipse. We have :

Simplifying this, we obtain :

3. From equations (1) and (2), we have :

4. Now, note that lines PQ and RS are perpendicular and pass through the origin, so PQ =2OP and RS = 2OR. Thus,

5. Substituting the values of r1 and r2, we obtain :

6. Hence, p= 13 and q = 144.

7. So, the final answer p + q = 13 + 144=157.

JEE Main Mock Test - 3 - Question 27

T is a point on the tangent to a parabola y2 = 4ax at its point P. TL and TN are the perpendiculars on the focal radius SP and the directrix of the parabola respectively. Then

Detailed Solution for JEE Main Mock Test - 3 - Question 27


*Answer can only contain numeric values
JEE Main Mock Test - 3 - Question 28

A bag contains six balls of different colours. Two balls are drawn in succession with replacement. The probability that both the balls are of the same colour is p. Next four balls are drawn in succession with replacement and the probability that exactly three balls are of the same colour is q. If p: q = m : n, where m and n are coprime, then m + n is equal to:


Detailed Solution for JEE Main Mock Test - 3 - Question 28

*Answer can only contain numeric values
JEE Main Mock Test - 3 - Question 29

If the mean and variance of four numbers 3, 7, x and y(x > y) be 5 and 10 respectively, then the mean of four numbers 3 + 2x, 7 + 2y, x + y and x - y is ______.


Detailed Solution for JEE Main Mock Test - 3 - Question 29

*Answer can only contain numeric values
JEE Main Mock Test - 3 - Question 30

Let S be the set of values of λ, for which the system of equations 
6λx - 3y + 3z = 4λ2,
2x - 6λy + 4z = 1,
3x + 2y + 3λz = λ has no solution. Then is equal to ___________.


Detailed Solution for JEE Main Mock Test - 3 - Question 30

Given that S be the set of values of λ for which given system of equations has no solution.

Therefore for the given set of equations

Also for each values of  we have

which implies that, for each values of λ, the given system of equations has no solution.

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