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Force is the external energy that is applied to an object. When we push or pull an object it is described as a force. Force is a vector quantity. The SI unit of force is Newton (N). The symbol for the representation of force is F. Power is the amount of energy that can be converted or transferred per unit of time. According to the International System of Units, the unit of power is 'watt' which is equal to 1 joule per second. Power is a scalar quantity because it doesn't possess direction.
| Table of Content |
Key takeaways: Force, Power, Vector, Scalar, Contact force, Non-contact force
What is Force?
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Force is applied to an object to change its velocity. The object tends to move from one place to another. It can be in both forms i. e. pull and push force. When we pull an object it changes its velocity and direction. The same happens in the other case i.e.pulling of an object. The force can be represented as F. The SI unit of Force is Newton (N).
F = ma (where m=mass and a= acceleration)
Force
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| Poisson's Ratio | Mechanical Properties of Solids | |
| Thermal Stress | Hooke’s Law | |
Types of Force
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There are various types of forces but they are categorised into two types i.e.
Contact force is defined as the force applied on the body in a straight manner or through any means. This is known as contact force.
The examples for Contact force are given below.
- Muscular Force
- Mechanical Force
- Frictional Force
Example: When a person goes to the gym he lifts so many weights and his muscles help him to lift the dumbbells. In this process, muscular force is applied by the person. Frictional force happens between a pair of surfaces in which one surface opposes the movement of the first surface over the second one.
Contact forces
Non-Contact force can be defined as the force applied on an object directly without making contact with the body.
Some of the examples of Non-contact Force are given below.
- Gravitational force
- Electrostatic force
- Magnetic force
Example: These types of force do not come in contact with the object directly and they exert a force from some distance.
Non-contact forces
What is Power?
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Power is the rate of doing work in a unit of time. This is represented as P. The SI unit of power is 'Watt'. Power is a scalar quantity. It has magnitude only. The formula is given by,
P= w/t (where w = work done and t = time taken per unit)
Power or energy can be calculated in Kilowatt (kW), Megawatt (MW) and Gigawatt (GW)
Power
We know Power is directly proportional to work and inversely proportional to time.
Mathematically, power is the dot product of two vectors, i.e. force and velocity.
Power = Force x Velocity
Power is a scalar quantity. The dimensional formula of power is ML2T-3
When force and velocity are given in magnitude its power = FVcos(θ).
Difference Between Force And Power
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The key differences between power and force are tabulated below.
| Force | Power |
|---|---|
| Whenever we apply a push or pull to an object then the push or pull is known as Force. | The rate of doing work per unit time is called power. |
| Represented by the symbol "F", its SI unit is Newton. | Represented by the symbol "P" and it's SI unit is Watt. |
| Formula for Force is given by, F = ma, where F = Force, m = mass and a = acceleration. | Formula for Power is given by, P= w/t ,where w = work done and t = time taken per unit . |
| For instance = when we are pushing a door to open it, we apply a force or when we are kicking a football we apply force. | For instance = We say a person is physically fit if he not only climbs four floors of a building but climbs them fast. Here we say that the person has climbed the stairs fast as he applied good power. |
Things to Remember
- Force is something that causes an object to move from one place to another. This can result in a change in the velocity of an object. The SI unit of force is Newton i.e.( N)
- There are some effects of force as follows. The ability to change the motion of an object, can either stop the object from moving or start to make it move, moving the body can change its direction along with their shape and size.
- Power is the rate of doing work in a unit of time. This is known as power. It is a scalar quantity. This only has a magnitude.
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Sample Questions
Ques. What do you mean by force? [2 marks]
Ans. Force is the external energy which can be applied to an object. When the force is applied it causes motion in the particular object.It starts to accelerate i. e.move from one place to another. This also affects their change in velocity. The SI unit of force is newton and is denoted by (N). Force can be represented as F.
Ques. What is the difference between force and power? [2 marks]
Ans. The concepts of both force and power sometimes convey similar meanings to each other. However, in the language of physics, both are interchangeable in which we can say force is typically the result of interaction between two objects whereas power is an expression of energy over time or work in which force acts as an element.
| Force | Power |
|---|---|
| Whenever we apply a push or pull to an object then the push or pull is known as Force. | The rate of doing work per unit time is called power. |
| Represented by the symbol "F", its SI unit is Newton. | Represented by the symbol "P" and it's SI unit is Watt. |
| Formula for Force is given by, F = ma, where F = Force, m = mass and a = acceleration. | Formula for Power is given by, P= w/t ,where w = work done and t = time taken per unit . |
| For instance = when we are pushing a door to open it, we apply a force or when we are kicking a football we apply force. | For instance = We say a person is physically fit if he not only climbs four floors of a building but climbs them fast. Here we say that the person has climbed the stairs fast as he applied good power. |
Ques. What is the relation between force and power? [3 marks]
Ans. As we know Force is equal to mass (m) and acceleration (a) which can be written as F = m × a
And Power is equal to work (w) divided by time (t)
P=W/t
= F ×s /t (where s is the distance)
Ques. What is the similarity between Work and Power? [2 marks]
Ans. The main similarity between Power and Work is that both are scalar quantities and show no direction.
Ques. What are the units of Power? [2 marks]
Ans. The Power or energy can be calculated in Kilowatt (kW), Megawatt (MW), and Gigawatt (GW)
Ques. Is weight a force? [2 marks]
Ans. Weight can be considered as a force and force is a type of vector quantity that shows both magnitude and direction associated with it. For example, an aeroplane flying in the sky is always directed towards the centre of the
earth.
Ques: What is the SI Unit for Force? [1 mark]
Ans. The SI Unit for Force is Newton(N).
Ques: What is the formula used to calculate Force? [2 marks]
Ans. Force is calculated using the following formula: F = ma
Where, F is the Force
m is the mass of the object
a is the acceleration
Ques: Write the Dimensional Formula for Power. [1 mark]
Ans. The dimensional formula for Power is ML2T-3
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