units and measurements jee questions

units and measurements jee questions

Welcome,
To STUDYEVERTHING
Today, we are going to cover the MOST IMPORTANT QUESTION from PHYSICS chapter PHYSICAL AND MEASUREMENT for exams like CBSE board, NEET, JEE MAIN & JEE ADVANCE.

First try to solve the question on your own in the allotted time (45 minutes). Then check the answers.

If you want to know the answers in detail you can simply download the pdf file which is at the end of the session.

So, what are you waiting for,
Let's crack it.

You may choose the language using translater, located at top of the right-hand side, as Hindi, Gujarati, etc.

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STUDY EVERTHING

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Section	no of questions	Alloted Time	Type	Question level
Type 1	10	same	Mcq	Moderate
Type 2	5	same	Integer	Moderate
Type 3	5	same	Mcq	Tough

Allotted time is same for all.

Quick Recap

Physical Quantities

The Quantities in terms of which laws of physics are expressed and which can be measured directly or indirectly.

Types of Physical Quantities 

1. Fundamental Quantities

(1). Length
(2). Mass
(3). Time
(4). Electric current
(5). Temperature
(6). Luminous Intensity
(7). Amount of substance

2. Derived Quantities

Velocity, acceleration, momentum etc.

Units

1. Fundamental Units

2. Derived units

Dimension of physical Quantities 

1. Velocity LT^-1
2. Acceleration LT^-2
3. Force MLT^-2
4. Work ML²T^-2
5. Kinetic energy ML²T^-2
6. Potential energy ML²T^-2
7. Torque ML²T^-2
8. Power ML²T^-3
9. Momentum MLT^-1
10. Impulse MLT^-1
11. Angle --
12. Strain --
13. Frequency T^-1
14. Angular velocity T^-1
15. Momentum of inertia ML²
16. Angular momentum ML²T^-1
17. Surface tension MT^-2
18. Spring constant MLT^-2
19. Surface energy MT^-2
20. Intensity MT^-3

Scalar Quantities 

Phyical quantities having only magnitude

Vector Quantities 

Phyical quantities having magnitude and direction and obey triangular law of vector addition. 

Dot product a.b=|a||b| cosθ

Cross product |a×b|=|a||b| sinθ

Errors 

Absolute Error δ = |a_mean -a_n| 

Relative Error =δa_mean /a_mean

Percentage error =δa_mean /a_mean ×100

Experiment

(a). Reading of screw gauge
Thickness of object =( mean scale reading)+ (circular scale reading)(least count)


Least count = pitch/ no. of circular division


(b). Reading of vernier calliper

Thickness of object =( mean scale reading)+ (vernier scale reading)(least count)

Least count =1MSD-1VSD

Significant figure

1. Non-zero digits are significant.

2. Zeros occurring between two non- zeros digits are significant.

3. In the number less than one, all zeros after decimal point and to the left of first non-zero digit are insignificant.

4. The terminal or trailing zeros in a number without a decimal point are not significant. 

TIMER:

45min

Type 1

1.Dimension of Planck constant is
a. MLT^-1
b.ML
c.ML²T^-1
d.LT

2.lenght of cube of side length 2.1×10^-2. It's volume is ___ ×10^-6
a.1.7
b.1.70
c.17
d.1700

3.A wire of length l=6+_-0.06cm and radius r=0.5+_-0.005cm and mass m=0.3+_-0.003gm. Maximum percentage error density is
a.1
b.4
c.2
d.6.8

4.The respective number of significant figures for the numbers 23.023,0.0003,2.1×10^-3.
a.5,1,2
b.5,1,5
c.5,5,2
d.4,4,2

5. Identify the pair whose dimension are equal.
a.torque & work
b.stress & energy
c.force & stress
d.force & work

6. SI unit of inductance,Henry can be written as
a.Weber/ampere
b..volt-sec/ampere
c.joule/(ampere)²
d.ohm-sec

7. Dimension of viscosity is
a.ML^-1T^-1
b. MLT^-1
c. ML^-1T^-2
d. ML^-2T^-2

8. Dimension of magnetic field is
a.MLT^-1
b. MT²
c. MT^-1
d. MT^-2

9. A vernier caliper has 1mm mark on main scale. It has 20 equal division Vernier scale which match with 16 main scale division.Find least count of this vernier caliper.
a.0.02mm
b.0.05mm
c.0.1mm
d.0.2mm

10.If planck constants h ,speed of light c,gravitational constant G are used to of unit of length L and unit of Mass M .Correct option is
a.M proportional to c^1/2
b.M proportional to G^1/2
c.L proportional to h^1/2
d.L proportional to G^1/2

TYPE 2      NUMERICAL TYPE

1.A body of mass m=3.153kg is moving along x axis with the speed of 5ms^-1.Calculate the magnitude of its momentum(kg ms^-1).

2.A screw gauge has 100 equal divisions and pitch of 1mm is used to measure the diameter of the wire of lenght 5.6cm the main scale. Find the curved surface area of the wire in cm² to appropriate significant figure.

3.In SI, the numberof basic physical quantites are

4.one light year equal to n× 10¹⁵m. Find 'n' ?

5.The density of soild ball is measured in experiment. The diameter of ball measured by screw gauge whose pitch is 0.5cm and there are 50 divisions on the circular scale. The reading on main scale is 2.5mm and that of circular scale is 20 division.If measure mass of the ball has error of 2%. The relative percentage error in density is______%.

TYPE 3    JEE ADVANCE

1.If n^th division of main scale coincide with (n+1)^th division of vernier scale given one main scale division is equal to 'a'units. Find the least count of vernier scale.
a.a/n+1
b.a/n-1
c.a(n+1)
d.a(n-1)

2.To find the distance d over which the signal can be seen clearly in foggy conditions a railway engineer uses dimension and assume that the distance speed depend on mass density ρ of the fog, intensity S of the light from the signal and its frequency f the engineer find that d is proportional to S^1/n.The value of n is
a.4
b.1
c.2
d.3

3.In the terms of potentialdifference V, electric current I, permittivity ε, permeabitily μ and speed of light c, then dimensionally correct is .
a.μI²=εV²
b.μI=εV
c.I=εcV
d.μcI=εV

4.The diameter of the cylinderismeasured using a vernier caliper with no zero error. It is found that zero errorof vernier scale is lies b/w 5.10cm and 5.15cm of the main scale. The vernier scale has 50 divisions equivalent to 2.45cm. The 24^th division exactly coincide with one of the main scale divisions. The diameter of the cylinder is
a.5.112cm
b.5.124cm
c.5.136cm
d.5.148cm

5.Using the value of 2dsinθ=λ one calculate the value of d by measuring the corresponding angle in θ in range 0° to 90°. The wavelength λ is exactly known error in θ Is constant for all values of θ. As θ increases from 0°
a.absolute error in d remains constant
b.absolute error in d increase
c.fractional error in d remains constant
d.fraction error decrease

Download the detailed answer pdf of the most important question of PHYSICAL AND MEASUREMENT.HERE.

Gravitation jee mains questions with solutions	click here
Kinamatic most important questions	click here
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Work, energy and power most important questions	click here
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Iiit cutoff	click here

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quantum entanglement experiment

Quantum entanglement
Quantum entanglement is a physical phenomenon that occurs when a pair or group of particles is generated, interact, in a way such that the quantum state of each particle of the pair cannot be described independently.
Two solve this problem Bohr and Einstein come up with new ideas.

Bohr theories of quantum world describe that Everything in this universe is based on chance or probability just like if a put a coin in a closed box then locked it.

 Then you may be wondering that it might be there or not which happens in the quantum world

• Einstein answered (jokingly): That means God is rolling dice.

Einstein doesn't not believe in probability actions.
 He wants to explore the world and always comes up with new ideas and theories. He predicted that there is a spooky action between two particles

Spooky action: let's take an example.
Suppose an Einstein has a pair of gloves.
He placed both right and left-hand gloves in separate and identical boxes.
You aren't aware that which inbox the Albert Einstein hides the right or left glove.

Now one of them is randomly picked up by you and another one shipped to Antarctica.
Now you open the box you found that it is right-handed glove then you think that others must be left-handed which is obvious. Similarly, the one quantum particle impacts the other.

But Bohr doesn't believe in spooky action. He predicted that there must be some natural force acted between two particles.
But Bohr failed to prove it.

• Bohr replied: Don't tell God what he has to do.

In 1975, an experiment was conducted and found that Bohr theories are correct.

Some natural forces acted between the particles but couldn't found how they interrelated. This whole scenario still a mystery.

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