Question

3. Answer the following questions: -
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a) Why is friction a necessary evil?
b) What is gravity?
c) What are the effects of force?
d) What is pressure?
e) What is reactivity series?
1) Why should grains be dried before storage?
g) What are pathogens?
h) Why are vaccines given to even a healthy persons?
i) What is penicillin?
i) What are weeds?​

Answer 1

1. Frictional force causes a lot of losses in general upkeep and wear and tear of machinery. Hence it is considered as a evil. But almost all crucial tasks cannot be carried out without the presence of friction. ... Hence it is considered as a necessary evil
2. the natural force that makes things fall to the ground when you drop them
3. A force acting on an object causes the object to change its shape or size, to start moving, to stop moving, to accelerate or decelerate.
4. Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. ... Pressure may also be expressed in terms of standard atmospheric pressure; the atmosphere (atm) is equal to this pressure, and the torr is defined as 1⁄760 of this.
5. SI unit: Pascal
6. In SI base units: 1 N/m2, 1 kg/(m·s2), or 1 J/m3
7. Derivations from other quantities: p = F / A
8. a reactivity series (or activity series) is an empirical, calculated, and structurally analytical progression of a series of metals, arranged by their "reactivity" from highest to lowest.
9. Presence of moisture and favourable temperature enhance germination of stored seeds. This should be controlled by removing the moisture completely
10. A pathogen is defined as an organism causing disease to its host, with the severity of the disease symptoms referred to as virulence. Pathogens are taxonomically widely diverse and comprise viruses and bacteria as well as unicellular and multicellular eukaryotes.

9. a substance that is used as a medicine (an antibiotic) for preventing and treating diseases and infections caused by bacteria

10. A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place". Examples commonly are plants unwanted in human-controlled settings, such as farm fields, gardens, lawns, and parks.