The SI unit for force is the Newton (N). A Newton is the force needed to cause a mass of 1 kilogram to accelerate at 1 m/s², so a Newton equals 1 kg ∙ m/s².

Undesirable plants that grow along with crop plants are known as weeds. Xanthium, Parthenium, etc. are some common weeds. Weeds compete with the crop for nutrients, light, and space. As a result, crop plants get lesser nutrients, light, and space for their development. This in turn, reduces their productivity. Thus, various weeding methods are employed.
Some important weeding methods are:

• Weeds can be controlled using weedicides. It is a chemical, which is sprayed in the fields to kill all available weeds. Weedicides are not harmful to crops.
• Tilling before sowing of crops also helps in removing weeds. Tilling uproots the weeds. The best time for the removal of weeds is before they produce flowers and seeds.
• The manual method of removing weeds is with the help of a khurpi. It involves regular uprooting or cutting of weeds close to the ground.

When white light is passed through a glass prism it splits into its spectrum of colours (in order violet, indigo, blue, green, yellow, orange and red) and this process of white light splitting into its constituent colours is termed as dispersion.

Transplanting is the process of moving a fully germinated seedling (or mature plant) and replanting it in a permanent location for the growing season. Transplanting is an important part of agribusiness in northern climates because it extends the flowering or fruit bearing season of many plants.

The Kharif cropping season starts with the onset of monsoon and ends when the rainy season is over. The rabi crops are sown at the end of monsoon and harvested before the advent of the summer season. These crops require good rainfall. The output of these crops depends upon the time and amount of rainwater. Paddy, maize, bajra, jowar are a few Kharif crops grown in India.

Following are some of the examples of Kharif crops:

• Rice
• Maize
• Sorghum
• Millets
• Ragi
• Soybean
• Cotton

The term food chain refers to the sequence of events in an ecosystem, where one organism eats another and then is eaten by another organism. It starts with the primary source like the sun or hydrothermal vents where producers make food, continues with consumers or animals who eat the food, and ends with the top predator.

A food chain is a sequence of events in nature in which one organism eats another, and is then eaten by another in turn. All food chains start with the primary source, either the sun or chemicals produced by hydrothermal vents deep in the ocean. When an organism uses those sources to make food, it starts the food chain.

Nitrogen fixation is the essential biological process and the initial stage of the nitrogen cycle. In this process, nitrogen in the atmosphere is converted into ammonia (another form of nitrogen) by certain bacterial species like Rhizobium, Azotobacter, etc. and by other natural phenomena.

Plants are the main of the sources of food. The nutrients obtained from plants are synthesized by plants using various elements which they obtain from the atmosphere as well as from the soil. This group of elements includes nitrogen as well. Plants obtain nitrogen from the soil through the process of protein synthesis. Unlike carbon dioxide and oxygen, atmospheric nitrogen cannot be obtained through stomata of leaves. Because the concentration of nitrogen gas present in the atmosphere can not be directly used by plants and also the concentration of the usable form of nitrogen in the atmosphere is very less. There are certain bacteria and some natural phenomenon which help in Nitrogen fixation.

Speed of the light is much higher than the speed of the sound. In normal conditions, the speed of the sound in air is just 332 m/s, but the speed of the light is 3×108 m/s. We can also observe this difference in our daily life during the phenomenon of lightning. When lightning occurs in the sky, the sound of the lightning comes after, but before we are able to see it in the sky. This proves that light waves travel faster and reach to us first and sound waves are slow, so we hear the sound of lightning later.

Before sowing the seeds, it is necessary to loosen and turn the soil in the fields as to break it to the size of the grains which is done with the help of three main implements or tools – plough, hoe and cultivator.

1. Plough: Plough is a large agricultural implement which is used for ploughing or tilling in the fields. The traditionally wooden plough consists of a long log of wood called a plough shaft having a handle at its one end. Below the handle is a strong triangular iron strip called ploughshare. The other end of the ploughshaft can be attached to a wooden beam which is fixed at the right angles to the ploughshaft.
2. Hoe: It is an agricultural implement used for removing weeds, and loosening and turning the soil. It consists of a long rod of wood or iron. There is a handle at one end of the hoe. A strong, broad and bent plate of iron is fixed below the handle and acts like a blade. The other end of hoe has a beam which is put on the neck of bullocks. Thus, a hoe is also pulled by animals like bullocks. Thus, it is a kind of modified plough.
3. Cultivator: The cultivator is a tractor driven agricultural implement which is used for loosening and turning the soil in the fields quickly. It has many ploughshares which can dig into the soil at the same time, loosen it and turn it. Thus, the field can be ploughed in a short duration of time.

In converting the temperature from Fahrenheit to Celsius the formula is, C = (5/9)(F – 32);

Mercury pollution is the pollution caused by the release of mercury from the mercury products or emissions from coal-burning power plants in air, water or land. Mercury pollution results in neurological and behavioural disorders in humans. Insomnia, memory loss, headaches, tremors are some of the symptoms of mercury pollution.

Pollution need not always be caused by chemical substances such as particulates (like smoke and dust). Forms of energy such as sound, heat or light can also cause pollution. These substances that cause pollution are called pollutants.

Smoke primarily consists of particles and can include other gaseous air pollutants, including nitrogen oxides, carbon monoxide, and hydrocarbons that may be toxic.

Inhalation exposures to nitric acid fumes involve exposure to nitric acid as well as nitrogen oxides such a nitrogen dioxide (NO2) and nitric oxide (NO).

Carbon monoxide (CO)—a colorless, odorless, tasteless, and toxic air pollutant—is produced in the incomplete combustion of carbon-containing fuels, such as gasoline, natural gas, oil, coal, and wood.

Blood is always red, actually. Veins look blue because light has to penetrate the skin to illuminate them, blue and red light (being of different wavelengths) penetrate with different degrees of success. What makes it back to your eye is the blue light.

Vaccines work on the principle of immunization. Vaccines help a body's immune system prepare in advance to fight infectious illnesses and potentially deadly diseases caused by infectious agents or their by-products. Vaccines ‘fool’ the immune system into developing a memory for a particular infection by putting something that mimics the microbe we want to vaccinate against, into the body. Many such vaccines are now available for preventing a number of infectious diseases, and provide a disease-specific means of prevention like tetanus, diphtheria, whooping cough, measles and polio.

In vitro fertilization is the most commonly used assisted reproductive technologies (ART). In vitro fertilization, as its name-fertilization is done by fusing ova from female donor and sperm from the male donor outside the body under strict laboratory conditions. This results in a zygote or famously known as test tube baby. After the embryo culturing, an embryo is transferred to the uterus of the mother. This method is commonly done in case of women with damaged or clogged Fallopian tubes.