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Difference between pressure and force is that both are inversely proportional to each other. When force is applied to a larger area, the pressure exerted is low and when force is applied to a smaller area, the pressure exerted is high.
- While force can be defined as the push and pull action resulting in the acceleration of an object, pressure is the force which is applied perpendicular to an object’s surface per unit area over which the force is distributed.
- The instrument which helps to measure force is known as a dynamometer.
- The two instruments that helps to measure pressure are Manometers and Barometers.
- In relation to atmospheric pressure, the barometer helps to measure pressure.
- However, a manometer measures the fluid pressure with respect to an outside source (typically the earth’s atmosphere).
Also Read: Potential Energy
| Table of Content |
Key Terms: Pressure, Force, Magnitude, Motion, Acceleration, Mass, Manometer, Surface area, External force, Velocity, Speed, Newton’s Laws of Motion
What is Force?
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Force is the push and pull movement on an object that has mass, causing it to change its velocity. It arises due to the physical interaction between two objects leading to a change in the present state of the object.
- Force is a vector quantity so it consists of both magnitude and direction.
- Both the magnitude and direction affect the state of the motion.
- Force is an external agent which is capable of changing the state of rest or motion of a body.
Force
- If more than one force is applied to an object then the resultant force is called the net force.
- When two different forces are applied in the same direction, then the resultant force is the sum of two forces.
- When two different forces are applied in the opposite direction, then the resultant force is the difference between the two forces.
There are many kinds of forces. Some of them are:
- Frictional Force
- Gravitational Force
- Magnetic Force
- Applied Force
- Buoyant Force
- Tension Force
- Drag Force
- Spring Force
A brief of force definition is:
| Type | Classification |
|---|---|
| Symbols | F→,F |
| SI unit of Force | Newton |
| SI base units | kg·m/s2 |
| Other Similar units | dyne, poundal, pound-force, kip, kilo pond |
| Derivations from other quantities: | F = m.a |
| Dimension of Force | LMT-2 |
How to Calculate Force?
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According to Newton’s Second Law of motion, the force applied by an object equals the mass times acceleration of that object. Mathematically, it can be denoted as:
| F = m x a |
Where,
- F = Force
- m = Mass
- a = Acceleration
Also Read:
| Related Articles | ||
|---|---|---|
| Effects of Force | Frictional Force | Joule Thomson Effect |
| Work Done | Work and Energy | Unit of Force |
What is Pressure?
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Pressure is the force acting perpendicularly on a unit area of a surface. It is defined as a force acting on a surface perpendicularly due to which the force spreads over that area.
- Pressure is measured by a Manometer.
- Pressure is a scalar quantity due to which it has only magnitude.
- The SI unit of pressure is Pascal (Pa) and is equal to one Newton per square meter. (N/m2 or kg/m1s2).
- If a force is applied to a large surface area, then the pressure is low.
- If force is applied to a small area, then the pressure is high.
The formula of Pressure is:
| Pressure (P) = Thrust/ Area |
Types of Pressure
Some of the types of Pressure includes:
- Atmospheric Pressure
- Absolute Pressure
- Differential Pressure
- Gauge Pressure
Force and Pressure Infographic
Read Also: Pascal’s Law and its Applications
How to Calculate Pressure?
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Pressure is the force spread over one object by the continuous pressing or pushing of two objects with each other. It can also be defined as the ratio of the force to the area (over which the force is acting).
Pressure Calculation
Mathematically,
| P = F/A |
Where,
- P = Pressure
- F = Magnitude of the external Force
- A = Surface area of the contacted surface
Differences between Force and Pressure
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The difference between Force and Pressure is:
| Force | Pressure |
|---|---|
| Force is the push and pull movement resulting in the acceleration of an object. | When force acts on a certain area positioned perpendicular to the surface of the object, pressure is exerted. |
| The standard unit is Newton and the symbol is N. | The standard unit is Pascal which is represented by Pa. |
| Force is measured by a Dynamometer. | Pressure is measured by a Manometer and Barometers. |
| It is a vector quantity. | It is a scalar quantity. |
| It has both magnitude and direction. | It only has magnitude. |
| Force can be applied to the faces, edges and vertices of the objects. | Pressure can only be exerted on the faces of the objects. |
| Force when applied to an object can change its velocity. | Pressure cannot change the velocity of the object it is applied to. |
Things to Remember
- Force is the push and pull that arises due to the physical interaction between two objects leading to the change in the present state of the object.
- It is a vector quantity and has both magnitude and direction.
- Pressure is the force acting perpendicularly on a unit area of a surface.
- When two different forces are applied in the same direction, then the resultant force is the sum of two forces.
- When two different forces are applied in the opposite direction, then the resultant force is the difference between the two forces.
- Mathematically, force is calculated by the formula- F = m x a
- The pressure is calculated by the formula- P=F/A
- Force is measured by a Dynamometer and Pressure is measured by a Manometer.
Also Check:
Sample Questions
Ques: Which law of motion gives the measure of force? (1 Mark)
Ans: Newton’s second law of motion gives the measure of force.
Ques: When a force is applied to a body, what are the two essential effects it can produce? (2 Marks)
Ans: The effects that a force produces when it is applied to a body are:
- It can bring a change in the state of motion or state of the rest of a body
- It can change the shape of a body.
Ques: Deduce Newton’s first law from the second law. (5 Marks)
Ans: According to Newton’s second law of motion
F = ma
m1 = \(\frac{F}{a_1} = \frac{5}{8} kg\)
m2 = \(\frac{F}{a_2} = \frac{5}{14} kg\)
M = \(( \frac{5}{8} + \frac{5}{24})kg = (\frac{5}{6})kg\)
Acceleration produced in M,
a = \(\frac{F}{M} = \frac {5}{5/6}\) = 6 ms– 2
If F = 0, a =0 since m ≠ 0,
But we know that:
a = (v−u)/t
or, v – u =0
so, v = u for whatever time t is taken.
This means that the object will continue moving with uniform velocity, u throughout the time, t. If u will be zero then v will also be zero. That is, the object will remain at rest.
Ques: What is the acceleration produced by a force of 12 newton exerted on an object of mass 3 kg? (2 Marks)
Ans: Given that- force, F = 12 N
Mass, m = 3 kg
We know that
F = m × a,
Putting the given values, we get
12 = 3 × a
a = 12/3 m/ s2
or, Acceleration, a = 4 m/s2.
Ques: A force of 500 N acts on a square piece of plywood, each of whose sides is 5 m long. Calculate the pressure acting on the piece of plywood. (2 Marks)
Ans: Given that-
Force acting on the square piece of plywood = 500 N
Area of the square piece = Side × Side = 5 m × 5 m
= 25 m2
Pressure acting on the piece of plywood = Force / Area
Pressure = 500 / 25
= 20 N/m2
Thus, the pressure acting on the square piece of plywood is 20 N/m2.
Ques: A force of 5 N produces an acceleration of 8 ms-2 on a mass m1 and an acceleration of 24 ms-2 on a mass m2. What acceleration would the same force provide if both the masses are tied together? (2 Marks)
Ans: Given that: F = 5 N or 5 kg ms-2
We know,
F= m x a
Thus, m1 = F/a1 = 5/5 kg
m2 = F/a2 = 5/24 kg
Therefore, M = 5/8 + 5/24 = 5/6 kg
The produced acceleration in M, a = F/M = \(\frac{5}{\frac{5}{6}}\) = 6 ms-2
Ques: What do you mean by pressure? Do liquids and gases also exert pressure? What is the SI unit of pressure? (2 Marks)
Ans: Pressure is defined as the Force per unit area (Force/Area). In other words, Pressure is the force acting perpendicularly on a unit area of a surface.
Yes, liquids and gases also exert pressure. The SI unit of Pressure is Pascal (Pa)
Ques: What are the effects of force on an object? (3 Marks)
Ans: The effects that a force exerts on an object are:
- Force can change the state of motion of an object.
- It changes the speed of a moving object.
- It can cause an object to turn or change direction.
- It can change the shape of an object.
Ques: What is pressure? What is the relation of pressure with the area on which it is applied? (2 Marks)
Ans: Pressure is defined as the force exerted per unit area. Pressure is related to the area on which it is applied. When the area is increased, less pressure is exerted on the object. But when the area on which pressure is exerted decreases, the pressure increases. So we can conclude that pressure increases with a decrease in area.
Ques: List the characteristics of pressure exerted by a liquid. (5 Marks)
Ans: Some of the basic characteristics of pressure exerted by a liquid are:
- Liquid exerts pressure in all directions.
- Pressure in liquid does not depend on the shape, size and surface area of the container.
- All points at the same level in a liquid are at the same pressure.
- Pressure increases with depth.
- Pressure does not depend on the surface of the immersed object.
Thus, it can be shown via:
Ques: A force of 400 N exerts a pressure of 20 N/cm2. What is the area on which the force acts? (3 Marks)
Ans: Given that-
Force = 400 N
Pressure = 20 N/cm2
We know that:
Pressure = Force/Area
So,
Area = Force / Pressure
Area = (400/20) cm2
= 20 cm2
Thus, the force is acting on an area of 20 cm2.
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