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COMEDK Mock Test - 8 - JEE MCQ


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30 Questions MCQ Test - COMEDK Mock Test - 8

COMEDK Mock Test - 8 for JEE 2024 is part of JEE preparation. The COMEDK Mock Test - 8 questions and answers have been prepared according to the JEE exam syllabus.The COMEDK Mock Test - 8 MCQs are made for JEE 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for COMEDK Mock Test - 8 below.
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COMEDK Mock Test - 8 - Question 1

Two massless springs with spring constants 2k and 9k carry 50 g and 100 g masses at their free ends. These two masses oscillate vertically such that their maximum velocities are equal. Then the ratio of their respective amplitude will be

Detailed Solution for COMEDK Mock Test - 8 - Question 1

COMEDK Mock Test - 8 - Question 2

Which of the following options are correct,
where i, j and k are unit vectors along the x, y and z axis?

Detailed Solution for COMEDK Mock Test - 8 - Question 2

Dot product of two different unit vectors is 0 and dot product of two same unit vectors is 1. Cross product of two different unit vectors taken according to right hand thumb rule is the other vector. Cross product of two same unit vectors is 0.

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COMEDK Mock Test - 8 - Question 3

An RC circuit as shown in the figure is driven by an AC source generating a square wave. The output wave pattern monitored by CRO would look close to:

Detailed Solution for COMEDK Mock Test - 8 - Question 3


For t1 - t2, Charging graph
For t2 - t3, Discharging graph

COMEDK Mock Test - 8 - Question 4

The velocity of the bullet becomes one third after it penetrates 4 cm in a wooden block. Assume that bullet is facing a constant resistance during its motion in the block. The bullet stops completely after travelling at (4 + x) cm inside the block. The value of x is:

Detailed Solution for COMEDK Mock Test - 8 - Question 4

COMEDK Mock Test - 8 - Question 5

A spherical hole is made in a solid sphere of radius R. The mass of the original sphere was M.The gravitational field at the centre of the hole due to the remaining mass is

Detailed Solution for COMEDK Mock Test - 8 - Question 5

By the principle of superposition of fields

Here  = net field at the centre of hole due to entire mass

 = field due to remaining mass

 = field due to mass in hole = 0

COMEDK Mock Test - 8 - Question 6

The half-life of Pa-218 is 3 minutes. What mass of a 16 g sample of Pa-218 will remain after 15 minutes?

Detailed Solution for COMEDK Mock Test - 8 - Question 6

Since 15 minutes = 5 x 3 minutes = 5 half-lives, the number of nuclei left after 15 minutes = 1/25 = 1/32 of the original number

Therefore, the mass of 16 g sample left after 15 minutes = 16/32 = 0.5 g

Hence, the correct choice is (d).

COMEDK Mock Test - 8 - Question 7

When a photon of light collides with a metal surface, number of electrons, (if any) coming out is

Detailed Solution for COMEDK Mock Test - 8 - Question 7

When photon strikes with the electron it completely transfers it’s energy to the electron as during photoelectric experiment the threshold frequency required is used by the electron to eject from the atom which is also called the work function and the remaining energy in electron is kinetic energy which can be measured. Now (before collision) since photon is a particle it must have mass and thus it has energy equivalent to E=mc2 .
After collision when it completely transfers it’s energy to electron thus E=0
And therefore 0=mc2 thus i guess photon vanishes.
 

COMEDK Mock Test - 8 - Question 8

Kinetic theory explains the behavior

Detailed Solution for COMEDK Mock Test - 8 - Question 8

Explanation:

The theory for ideal gases makes the following assumptions

1. Gases consist of particles in constant, random motion. They continue in a straight line until they collide with something—usually each other or the walls of their container.

2. Particles are point masses with no volume. The particles are so small compared to the space between them, that we do not consider their size in ideal gases.

3. No molecular forces are at work. This means that there is no attraction or repulsion between the particles.

4. Gas pressure is due to the molecules colliding with the walls of the container. All of these collisions are perfectly elastic, meaning that there is no change in energy of either the particles or the wall upon collision. No energy is lost or gained from collisions.

5. The time it takes to collide is negligible compared with the time between collisions.

6. The kinetic energy of a gas is a measure of its Kelvin temperature. Individual gas molecules have different speeds, but the temperature and kinetic energy of the gas refer to the average of these speeds.

7. The average kinetic energy of a gas particle is directly proportional to the temperature. An increase in temperature increases the speed in which the gas molecules move.

8. All gases at a given temperature have the same average kinetic energy.

9. Lighter gas molecules move faster than heavier molecules.

COMEDK Mock Test - 8 - Question 9

A jar is filled with two non-mixing liquids 1 and 2 having densities respectively. A solid ball, made of a material of density , is dropped in the jar. It comes to equillibrium in the position shown in the figure.

Which of the following is true for  

[AIEEE 2008]

                

Detailed Solution for COMEDK Mock Test - 8 - Question 9

The density of ball should be greater than liquid 1 because it sinks in it.
Also density of ball should be less than density of liquid 2 as it floats on it.

COMEDK Mock Test - 8 - Question 10

A bar magnet of length 14 cm is placed in the magnetic meridian with its north pole pointing towards the geographic north pole. A neutral point is obtained at a distance of 18 cm from the centre of the magnet. If BH = 0.4G, the magnetic moment of the magnet is (1 G = 10-4 T)

Detailed Solution for COMEDK Mock Test - 8 - Question 10


i.e. 
= = 0.4 × 10-4
⇒ 
= 0.4 × 10-4

M = m × 14 cm = m × 14/100

= 4 × 10-4 × 7203.82 = 2.88 J/T

COMEDK Mock Test - 8 - Question 11

Propyne on hydrolysis in presence of HCl and HgSO₄ gives

COMEDK Mock Test - 8 - Question 12

Point out the incorrect statement about resonance?

COMEDK Mock Test - 8 - Question 13

Which of the following favours the backward reaction in a chemical equilibrium?

COMEDK Mock Test - 8 - Question 14

A reaction reaches a state of chemical equilibrium only when

COMEDK Mock Test - 8 - Question 15

The effective atomic number of Cr (at. no. 24) in [(Cr(NH₃)₆] Cl₃ is

COMEDK Mock Test - 8 - Question 16

At cathode, the electrolysis of aqueous Na₂SO₄ gives

COMEDK Mock Test - 8 - Question 17

How many litres of O₂ at STP are needed to complete the combustion of 39 g of liquid benzene as per equation given below ?
2C₆H₆(l) + 15O₂(g) →12CO₂(g) + 6H₂O(g)

COMEDK Mock Test - 8 - Question 18

A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressures of the pure hydrocarbons at 20oC are 440 mm of Hg for pentane, and 120 mm of Hg for hexane. The mole fraction of pentane in the vapour phase would be

Detailed Solution for COMEDK Mock Test - 8 - Question 18

Total vapour pressure (VP) of mixture = VP of pentane in mixture + VP of hexane in mixture
PT = (Mole fraction of pentane × VP of pentane) + (Mole fraction of hexane × VP of hexane)
PT = 
VP of pentane in mixture = VP of mixture × Mole fraction of pentane in vapour
88 = 184 x Mole fraction of pentane in vapour
Or, mole fraction of pentane in the vapour phase = 88/184 = 0.4782 

COMEDK Mock Test - 8 - Question 19

10 mL10 mL of 0.1 M CH3COONa+ is mixed with11 mL 0.1 M HCl of the concentration of CH3COO ion at equilibrium is, (take Ka(CH3COOH) = 10−5)

Detailed Solution for COMEDK Mock Test - 8 - Question 19


 due to common ion effect.
x⋍10−4M

COMEDK Mock Test - 8 - Question 20

The sentence "____ if and only if x + x = 3x" is TRUE.

Detailed Solution for COMEDK Mock Test - 8 - Question 20

"if and only if" is TRUE when both conditions are the SAME truth value. Since "x + x = 3x" is false, the first condition must also be false. 2x - x = 2x is false.

COMEDK Mock Test - 8 - Question 21

If A and B are two matrices such that AB=B and BA=A, then A2+B2=

COMEDK Mock Test - 8 - Question 22

The area of the curve |x|+|y|=4 is

COMEDK Mock Test - 8 - Question 23

If xy=e(x-y), (dy/dx)=

COMEDK Mock Test - 8 - Question 24

If n is any odd number, which of the following is true about n +1?

Detailed Solution for COMEDK Mock Test - 8 - Question 24

Every whole number is either odd or even.
A whole number is even if it can be divided evenly by two; the numbers 2, 4, 6, 8, 10, 12, . . . are even.
In this question we are given the information that n is an odd number.
Because n is odd, it must be one of the numbers 1, 3, 5, 7, 9, 11, 13, 15, and so on.
Now we have to reason mathematically.
If n is a member of this “odd” list, then what can we say for sure about n +1?
If we add 1 to each number in the odd list, we get the “ n +1 ” list: 2, 4, 6, 8, 10, 12, 14, 16, and so on, which are even numbers.

COMEDK Mock Test - 8 - Question 25

If A = [x y z] ,  

then [ a x2 + b y2 + c z2 + 2 hxy + 2 gzx + 2 fyz ] is

COMEDK Mock Test - 8 - Question 26

The number of parallelograms that can be formed from a set of four parallel lines intersecting another set of there parallel lines is :

Detailed Solution for COMEDK Mock Test - 8 - Question 26

COMEDK Mock Test - 8 - Question 27

If the matrix  is singular, then θ =

Detailed Solution for COMEDK Mock Test - 8 - Question 27

COMEDK Mock Test - 8 - Question 28

The ratio in which the plane r̅.(i̅−2j̅+3k̅)=17 divides the line joining the points -2i̅+4j̅+7k̅ and 3i̅+5j̅+8k is̅

COMEDK Mock Test - 8 - Question 29

The equation of the parabola whose focus is (1,-1) and directrix is x + y + 7 = 0 is

COMEDK Mock Test - 8 - Question 30

The vertex of the parabola
y2 = 4(a' - a) (x - a) is

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