Question

How is pressure related to force?
A. Directly proportional
B. Inversely proportional
C. Either A or B
D. Neither A nor B

Answer 1

Hint: State the basic definition of force and pressure. Use the equation,
\[P=\dfrac{F}{A}\] to find the relation between pressure and force. Check whether they are directly proportional.

Complete step by step answer:
Force: Whenever someone asks you about force, suddenly you will give the definition of force as it is the push or pull on an object by another because the force was introduced to us as this in our earlier school days. But when we come to higher classes, we learn it in another aspect i.e. it is the result of interaction between more than one object. It is the cause of the change of state of the motion of an object.

In addition to this don’t forget that it is a vector quantity, which has both direction and magnitude. The SI unit of force is Newton (N).

Pressure: Whereas we can simply state that pressure as it is the force applied on an object per unit area. From the above definition we can mathematically express the equation for force as

\[Pressure=\dfrac{Force}{Area}\]
\[P=\dfrac{F}{A}.........(1)\]

where P is the pressure
F is the force and
A is the unit area.
(Unit area is the area of the square whose length is 1m in SI unit system).
Its unit is Pascal (Pa).

From equation (1) it is evident that as force increases, pressure also increases and as force decreases pressure also decreases since force is in the numerator. Or pressure is directly proportional to the applied force.

i.e. P α F

Whereas as the area increases, the pressure decreases. i.e. it increases with the decrease in area. Since area in the denominator, we can say that it is inversely proportional pressure.
In our day to day life we have come across situations like this several times. For example, consider the case of a knife with a sharp edge and blunt edge. Therefore, we can say that option A is the answer.

Note: Even though force is a vector quantity, pressure is not because it acts in all directions. Whereas thrust is a vector quantity since, forces that are perpendicular to the surface are taken in account.