Question

What is relationship between pressure, force and area? Explain, using  your understanding of pressure, why a sharp knife cuts better than a blunt knife.​

Answer 1

Answer:

There is a relationship between pressure,force and area ,the relationship is as follows -

1 . pressure decreases as area increases and it increases as area decreases .

2 .and also as force increases the pressure increases and when the force decreases the pressure decreases, and pressure cannot exist without force.

3 and also force is inversely proportional to area.

The sharp knife cuts better than the blunt knife because the sharper the knife the less the area of contact between the knife and the surface to be cut and we already know the lesser the area of contact the more the pressure hence the sharp knife cuts better than the blunt one.

Answer 2

Answer:

pressure =$\frac{thrust}{area\\}$

Explanation:

Have you ever wondered why a camel can run

in a desert easily? Why an army tank weighing

more  than  a  thousand  tonne  rests  upon  a

continuous chain? Why a truck or a motor bus

has much wider tyres ? Why cutting tools have

sharp  edges?  In  order  to  address  these

questions  and  understand  the  phenomena

involved, it helps to introduce the concepts

of the net force in a particular direction (thrust)

and the force per unit area (pressure) acting

on the object concerned.

Let us try to understand the meanings of

thrust  and  pressure  by  considering  the

following situations:

Situation  1:  You  wish  to  fix  a  poster  on  a

bulletin board, as shown in Fig 10.3. To do

this task you will have to press drawing pins

with  your  thumb.  You  apply  a  force  on  the

surface area of the head of the pin. This force

is directed perpendicular to the surface area

of the board. This force acts on a smaller area

at the tip of the pin.

Situation 2: You stand on loose sand. Your

feet go deep into the sand. Now, lie down on

the sand. You will find that your body will not

go that deep in the sand. In both cases the

force exerted on the sand is the weight of your

body.

You have learnt that weight is the force

acting vertically downwards. Here the force

is acting perpendicular to the surface of the

sand.  The  force  acting  on  an  object

perpendicular to the surface is called thrust.

When you stand on loose sand, the force,

that is, the weight of your body is acting on

an area equal to area of your feet. When you

lie down, the same force acts on an area equal

to the contact area of your whole body, which

is larger than the area of your feet. Thus, the

effects  of  forces  of  the  same  magnitude  on

different  areas  are  different.  In  the  above

cases,  thrust  is  the  same.  But  effects  are

different.  Therefore  the  effect  of  thrust

depends on the area on which it acts.

The effect of thrust on sand is larger while

standing than while lying. The thrust on unit

area is called pressure. Thus,

$\frac{thrust}{pressure}$ = area (10.20)

Substituting the SI unit of thrust and area in

Equation (10.20), we get the SI unit of pressure as

N/m2 or N m–2.

In honor of scientist Blaise Pascal, the

SI unit of pressure is called pascal, denoted

as Pa.

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