Let v be the velocity of the girl on the cart as the cart starts moving.
The total momenta of the girl and cart before the interaction = (50 x 5 m s-1) + (4 x 0 m s-1)

                                                                            = 250 kg m s-1
The total momenta after the interaction = (50 + 4) kg x v m s-1

                                                               = 54 v kg m s-1
According to the law of conservation of momentum,
Total momentum before the interaction = Total momentum after the interaction

→ 54 v = 250

v = 250/54 = 4.62 m/s

Albert Einstein was really a scientific genius. He felt at home in Mathematics but he showed keen interest in physics. After graduating from the university in Zurich he started working vigorously. With his university education he was working on relativity.

Albert Einstein was born on 14th March in 1879, in the German city of Ulm. Till the age of two and half years, he could not speak and when he started speaking, he spoke every word twice. His playmates considered him to be boring and his mother thought that he was crazy because of the abnormally large size of his head.

The Mass per cent formula is expressed as solving for the molar mass also for the mass of each element in 1 mole of the compound. You can determine the mass percentage of each element with these masses.

Following are the formula of projectile motion which is also known as trajectory formula:

Where,

• V_{x  is} the velocity (along the x-axis)
• V_xo is Initial velocity (along the x-axis)
• V_y is the velocity (along the y-axis)
• V_yo is initial velocity (along the y-axis)
• g is the acceleration due to gravity
• t is the time taken

The primary function of striated muscles is to generate force and contract in order to support respiration, locomotion, and posture (skeletal muscle) and to pump blood throughout the body (cardiac muscle).

Skeletal(Striated) Muscle:
Structure: Skeletal muscle is called "striated" because of its appearance consisting of light and dark bands visible using a light microscope. A single skeletal muscle cell is long and approximately cylindrical in shape, with many nuclei located at the edges (periphery) of the cell.

Function: 

• Movement of the skeleton under conscious control, including movement of limbs, fingers, toes, neck, etc.
• Movement of tissues of facial expression under conscious control, e.g. ability to smile and to frown.

HRD Minister Ramesh Nishank announced a major CBSE syllabus reduction for the new academic year 2020-21 on July 7 which was soon followed by an official notification by CBSE on the same.

Considering the loss of classroom teaching time due to the Covid-19 pandemic and lockdown, CBSE reduced the syllabus of classes 9 to 12 with the help of suggestions from NCERT.

Click on the given links for deleted syllabus:

• <a href="http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/Deduction/DELETEDComputer_Application_Sec_2020-21.pdf" target="_blank">Deleted - Computer Application</a>
• <a href="http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/Deduction/DELETEDEnglish_Sec_2020-21.pdf" target="_blank">Deleted - English - Language and Literature</a>
• <a href="http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/Deduction/DELETEDHindi_A_Sec_2020-21.pdf" target="_blank">Deleted - Hindi A</a>
• <a href="http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/Deduction/DELETEDHindi_B_Sec_2020-21.pdf" target="_blank">Deleted - Hindi B</a>
• <a href="http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/Deduction/DELETEDHome_Science_Sec_2020-21.pdf" target="_blank">Deleted - Home Science</a>
• <a href="http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/Deduction/DELETEDMathematics_Sec_2020-21.pdf" target="_blank">Deleted - Mathematics</a>
• <a href="http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/Deduction/DELETEDScience_Sec_2020-21.pdf" target="_blank">Deleted - Science</a>
• <a href="http://cbseacademic.nic.in/web_material/CurriculumMain21/revisedsyllabi/Deduction/DELETEDSocial_Science_Sec_2020-21.pdf" target="_blank">Deleted - Social Science</a>

Crop protection is the general method or the practice of protecting the crop yields from different agents including pests, weeds, plant diseases, and other organisms that cause damage to the agricultural crops.

Apart from crops, agricultural fields would have weeds, small animals like rats, mites, insects, pests, disease-causing pathogens and frequently raided by birds. All these factors are mainly responsible for the loss or damage to the crops. Thus to yield high crop production, farmers need to protect the crop from these pests. Hence crop protection management is important before, during and after the cultivation.

Crop protection is the general method or the practice of protecting the crop yields from different agents including pests, weeds, plant diseases, and other organisms that cause damage to the agricultural crops.

Apart from crops, agricultural fields would have weeds, small animals like rats, mites, insects, pests, disease-causing pathogens and frequently raided by birds. All these factors are mainly responsible for the loss or damage to the crops. Thus to yield high crop production, farmers need to protect the crop from these pests. Hence crop protection management is important before, during and after the cultivation.

The momentum is zero.

Explanation:

momentum is the product of mass and velocity of a particular material . And when ball is thrown vertically upwards its velocity at highest point is zero . Therefore momentum P = m× v = m × 0 =0.

Isotopes: Isotopes are atoms with the same number of protons but that have a different number of neutrons. Since the atomic number is equal to the number of protons and the atomic mass is the sum of protons and neutrons, isotopes are elements with the same atomic number but different mass numbers.

Isobars: Atoms of different elements with different atomic numbers, which have the same mass number, are known as isobars.

Movement of any object from one position to another position with respect to the observer is called as Motion.

In 1911 Rutherford made and experiment to study about the structure of atom. In this experiment the α-particles from ₈₃Bi²¹⁴ (a radioactive source) contained in a lead cavity are collinated into a narrow beam with the help of a lead plate having a narrow slit the narrow beam of α-particles then falls on a thin gold foil (about 2.1 x 10^-10 m thick). The α-particles scattered in different directions.The whole apparatus was arranged inside a vaccum chamber toprevent the scattering of α-particles from air molecules. The experimental observations led Rutherford to the following conclusions-

(i) Since most of the α-particles passed undiviated, than atom has a lot of empty space in it. 

(ii) Since the fast and the heavy α-particle could be deflected through even 180°, the whole of + ve charge and partcially the entire mass of the atom was confined to an extremely small central core. 

It was called nucleus. 

Since 1 in about 8000 α-particles in deflected through 180°, the size of the nucleus is about 1/10,000 th of the size of the atom.

(iii) The scattering of different α-particles through different angles on the nuclear model of the atom as below.

The α-particles such as a and a',which pass through the atom at a large distance from the nucleus experiences a small electrostatic force of repulsion due to the nucleus and hence undergo a very small deflection. The α-particles b and b¹ which pass through the atom at a close distance from the nucleus suffer a large deflection.The α-particles such as C, which travels towards the nucleus directly, shows down as it moves and ultimately comes to rest and than after being deflected through 180°, retraces it path.

2. 

Let the mass of earth = M.

Let the mass of the object = m.

Distance between the the earth's centre and object = Radius of the earth = R.

Therefore,

Gravitational Force = F = GMm/ R ²

1. Newton's law of universal gravitation states that a particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

In a Plant cell, Plastids are the largest cell organelle.

Nucleus



 Nucleus is the largest organelle. Nucleus is present in the eukaryotic cells.

 Nucleus holds the genetic material. The shape of the nucleus is spherical.

 Nucleus regulates all the activities of the cell. Therefore, it is called as the 



 Protoplasm

 Plasma membrane



 Cytoplasm

 Nucleus

 Cytoplasm is the cellular matrix, in this matrix the nucleus is suspended.

Phosphorus(Atomic no. 15) has its electrons arranged in a configuration of 2,8,5. Now, orbits are stable when they are full. In this case, The outer orbit must have eight electrons for stability in combining with other elements, also known as valency. So one can either add 3 electrons to the outer orbit or take away 5 electrons with equal ease. So Phosphorus has a valency of 3 or 5.