The Correct answer is J. J. Thomson.

Key Points

• A British physicist J.J.Thomson Heightened the theory of Dalton.
• Thomson found the existence of extremely minute particles inside the atom.
• He compared the atom with a 'watermelon' in which the Red part resembles the positively charged portions while the black seed resembles the negatively charged electrons.
• The atom itself is neutral in nature, as it has equal positive and negatively charged electrons.
• Thomson discovered 'Electrons' for which he got Nobel prize in 1906 A.D.
• Thomson proposed a better atomic theory than Dalton's atomic model.
• According to him, a positive charge is dispersed everywhere and the idea that atoms are made up of negative electrons embedded in a gel of positive charge was wrong.
• Electrons were accidentally discovered by J. J. Thomson while studying the cathode rays.
• The name electron was given by 'stony'.
• Cathode rays are emitted from the cathode in a straight line if these rays strike on metal objects there is the formation of 'X-rays'.

Additional Information

James Chadwick-

• Sir James Chadwick was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932.
• By 1920, physicists knew that most of the mass of the atom was located in a nucleus at its center and that this central core contained protons.
• In May 1932 James Chadwick announced that the core also contained a new uncharged particle, which he called the neutron.

Rutherford-

• Rutherford overturned Thomson's atom model in 1911 with his well-known Gold Foil experiment.
• Rutherford made an experiment, he beamed alpha particles through a thin gold foil. From this, he came to know that:
  • Most alpha particles passed through the gold foil, very few particles bounced back exactly towards the source.
  • Some of the particles deviate at various angles.
  • He concluded that an atom has a tiny, dense, 'positively charged' core, where all mass is concentrated; known as Nucleus.
  • The thickness of gold foil - 0.00004 cm.
  • Alpha particle - A helium nucleus.

John Dalton-

• In 1803 A.D. he put forth his famous atomic theory.
  • The matter is made up of small particles called atoms.
  • Atoms can not be created, divided into smaller particles, nor destroyed in the chemical process.
  • Atom is a rigid and massive ball-like structure.

Given:- 

25 percent of 40 percent of (2/7) of 2100

= (25/100 ) × (40/100) × (2/7) × 2100 = 60

∴ The required answer is 60.

According to the given information:

One evening before sunset, two friends F1 and F2 were talking while looking at each other. If F1's shadow was to his immediate right, then the following diagram can be drawn:

Thus, F2 is facing 'South' direction.

Hence, the correct answer is "South".

The correct answer is For an electron to remain in its orbit, electrostatic attraction between an electron and the nucleus which tends to pull the electron towards the nucleus must be equal to the gravitational force

Concept:-

• Bohr's Theory: Bohr's theory is a model of the atom that was proposed by Niels Bohr in 1913.
• Electrostatic Force: The electrostatic force is the force of attraction or repulsion between two charged particles.
• Gravitational Force: The gravitational force is the force of attraction between two objects with mass.

Explanation:-

• Bohr's theory was a revolutionary model for its time, but it has since been superseded by quantum mechanics.
• Quantum mechanics is a more complete and accurate theory of the atom.
   
• The three main postulates of Bohr's theory are:

1. Electrons orbit the nucleus in circular paths called shells.
2. The energy of each shell is quantized, meaning that it can only have certain discrete values.
3. An electron can move from one shell to another by absorbing or emitting a photon of light with an energy equal to the difference in energy between the two shells.

Bohr's theory does not take into account the gravitational force between the electron and the nucleus. The gravitational force between these two particles is negligible compared to the electrostatic force.

Conclusion:-

The statement that stands false for Bohr's Theory is that the electrostatic attraction between the electron and the nucleus must be equal to the gravitational force.

Given:

Diameter of cylinder = 35 cm

Curved surface area = 3080 cm²

Formula used:

Radius = Diameter/2

Curved surface are of cylinder = 2πrh

Volume of cylinder = πr²h

where r = radius , h = height

Calculation:

Diameter (d) = 35 cm

⇒ Radius = d/2

⇒ 35/2

⇒ Radius = 17.5

Curved surface area of cylinder = 2πrh = 3080

⇒ 2 × 22/7 × 17.5 × h = 3080

⇒ h = 28 cm

Now Volume of cylinder = πr2h

⇒ 22/7 × (17.5)² × 28

⇒ 22 × 306.25 × 4

⇒ 26,950 cm³ 

∴ Volume of cylinder is 26,950 cm³.

The family tree is given below:-

• Z is the brother of P.

Hence, "option 3" is the correct answer.

The correct answer is 8th march.

Key Points

• International Women's Day is celebrated on 8th March.
• International Women's Day is a global day celebrating  the social, economic, cultural, and political achievements of women.
• The day also marks a call to action for accelerating gender parity.
• This year's theme for International Day is "Women in leadership: Achieving an equal future in a COVID-19 world".

Important Points

• National Women's Day- 13 February
• National Girl Child Day- 24 January
• International Day of the Girl Child- 11 October

Additional Information

The correct answer is Newton's first law.

CONCEPT:

• Newton’s first law of motion: It is also called the law of inertia. Inertia is the ability of a body by virtue of which it opposes a change.
• According to Newton’s first law of motion, an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
• The inertia of rest: When a body is in rest, it will remain at rest until we apply an external force to move it. This property is called inertia of rest.
• The inertia of motion: When a body is in a uniform motion, it will remain in motion until we apply an external force to stop it. This property is called inertia of motion.

EXPLANATION:

• When a bus suddenly starts moving, the passengers fall backward due to the law of inertia of rest or 1st law of Newton.
• Because the body was in the state of rest and when the bus suddenly starts moving the lower body tends to be in motion, but the upper body still remains in a state of rest due to which it feels a jerk and falls backward. Hence option 1 is correct.

Additional Information

Laws of Motion given by Newton are as follows:

Given:

Time interval between each bus = 50 minutes

Mohit's speed = 50 km/hr

Time between each meeting with a bus = 10 minutes

Concept:

Relative speed is the rate at which the distance between the two objects is changing with respect to time.

Solution:

Let speed of the bus is x km/hr

Distance covered by bus in (50 - 10) = 40 minutes = The distance travelled by Mohit in 10 minutes

Distance covered by bus in 40/60 = The distance travelled by Mohit in 10/60

40x/60 = 50 × 10/60

x = 12.5

Therefore, the speed of the bus is 12.5 km/hr.

The logic that follows here is:

Therefore, there are 15 parallelograms are present in this figure.

Hence, the correct answer is 15.