Defining Force, Its Formula, Unit and Effects
Force is defined as an external cause that changes or tends to change the state of the body once applied. If the body is in motion, it comes to rest, and if at rest, then it will come to motion. It can also cause a change in the direction, shape, size, etc., of the body. Pushing or pushing a door with force is an example. Force is a vector quantity, meaning it has both magnitude and direction. Newton's second law defines force as the "product of a body's mass and acceleration."
Example: The fact that a push or a pull is referred to as a force should be emphasised as a primary focus of your instruction at this level. There are several instances of forces in our daily lives. For example: weight force (the weight of something). It is the force exerted by a bat on a ball, and the power of the hairbrush on the hair during brushing.
Definition of Force
Force is defined as the pushing or pulling of an item. Push and pull are caused by the interaction of two things. Force may also be expressed using terms like stretch and crush.
A force is an external agent that may change the condition of rest or motion of a body. It has a magnitude as well as a direction. The direction of the force is the place where force is applied, and the application of force is the location where force is applied.
The Formula of Force
The vector product of mass (m) and acceleration (a) expresses the quantity of force. The equation or the formula for force may mathematically be stated in the form of :
\[F = ma\]
Where \[m\]= mass, \[a\]= rate of acceleration
It is expressed in Newtons (N) or kilograms per square metre per second\[(Kgm/{{s}^{2}})\].
Unit of Force
The force applied on an object is measured in terms of Newton and dyne. Force is measured in dyne in the centimetre gram second system of unit (CGS unit). It is represented in Newton (N) in the standard international system of units (SI unit).
Dyne and Newton are related to one another. We can convert the value of force in dyne and newton using the relationship between them. The value of dyne in terms of newton and vice versa is as given below:
1 dyne = \[1{{0}^{-5}}~\]newton
1 Newton =\[~1{{0}^{5}}~\]dyne
Newton: 1N can be defined as the force required to move an object with a mass of 1 kg at an acceleration of \[1\text{ }m/{{s}^{2}}.\]. It is represented by letter N. Mathematically, we write:
\[\mathbf{1N}=1kg\times 1m/{{s}^{2}}\]
1 Dyne: It is the force required to course an object with a mass of 1 gram at an acceleration of 1 cm/s2. Mathematically we write:
\[1~dyne=1g\times 1cm/{{s}^{2}}\]
How Force Can Change the Shape of an Object
When a force is exerted on an item, it might change form by bending, stretching, or compressing-or by a combination of all three.
Force can Change the Shape
Compression forces that change the shape of objects include
Forces acting on the walls of an inflated balloon when it is pressed between our hands
The force required to roll chapati or roti dough
The force that is exerted on a spring or a rubber band when it is stretched
The force created by a collision between two moving vehicles
Effects of Force
Forces acting on a body can change the shape of the body, accelerate or decelerate it, give motion to the static body, or stop the motion of the dynamic body.
The force effect can be explained by the following:
The force either increases the speed of a moving object or moves a stationary object.
A force can either stop or reduce the speed of a moving object.
The force effect causes the object's direction to change.
The object's shape and size are altered by force.
Force Can Change the Direction of a Moving Object
How can force be used to change the direction of a moving object? When an external force acts on a freely moving object, its direction will change.
Some examples are given below:
When you hit a cricket ball, its direction changes.
When a batsman hits the ball with his bat, the speed of the ball changes.
When a person applies the brakes in a car, the vehicle comes to a stop with a decrease in speed.
The speed of the ball decreases when the fielder catches it.
When we pull the trolley, its speed increases.
Force Can Change the Speed of a Moving Object
When a force is applied to a body, the body accelerates and acceleration alters the body's speed. A force may modify the speed of a moving item, the direction of a moving object, and the form and size of an object, but it cannot change the composition of a moving object.
Some examples are given below:
When a driver accelerates his car while it is in motion, the vehicle's speed increases.
When a person uses the brakes in a car, the vehicle comes to a complete stop with a drop in speed.
What a Force Can Do
Forces may cause things to accelerate, decelerate, stop, start, change direction, shape, or even spin. Let’s discuss how it does so!
Change Direction and Accelerate: Imagine kicking a ball that is slowly approaching you. It will not only go quicker (accelerate), but it may also change direction if you hand it to someone.
Stop: A force acting on an object causes it to change shape or size, begin or stop moving, accelerate or decelerate. When two objects interact, they exert a force on each other; these exerted forces are equal in size but opposite in direction. Eg: Imagine a goalie using power to deflect a ball that is heading towards him.
Get Moving: When a force pushes or pulls on an object, it moves in the same direction as the force. The greater the acceleration, the greater the force and the lighter the object. It can also cause something to slow down, accelerate, or change direction.
Shape Change: When a force acts on an object, it can change shape by bending, stretching, or compressing - or by a combination of all three. Changing the motion of objects is the responsibility of forces. The shape of an object can change if more than one force is present.
Turning: Forces are required to turn or spin things. When left to their own devices, moving objects move in straight lines. It takes a lot of force to get them to turn in a circle instead. Larger forces are required to turn heavier objects, spin them faster, or make them turn in tighter.
Solved Problems
1. Michael uses 30N of power to push a 2kg box to the left. Annie uses 40N of force to push the same box to the right. What is the box's net force?
Possible responses:
a)1.33N
b)10N
c)−10N
d)0.75N
Ans. We sum together all the forces to get the net force:
\[{{F}_{net}}={{F}_{Michael}}+{{F}_{Annie}}\].
Since force is a vector, the direction of action is important. We shall turn leftward motion into a negative and rightward motion into a positive. Michael is pushing to the left with\[30N\], hence his force is\[30N\]. Annie was pushing to the right with\[40N\], thus her force will stay 40N.
We can get the net force by summing the individual force together.
\[{{F}_{net}}={{F}_{Michael}}+{{F}_{Annie}}\]
\[{{F}_{net}}=-30N+40N\]
\[{{F}_{net}}=10N\]
2. Aimee's toy car weighs 2 kg. How much force should she apply to the car in order for it to go at an acceleration of\[8 m/{{s}^{2}}\]?
Ans.
Given:
m (toy car mass) = \[2\] Kg
a = \[8m/{{s}^{2}}\](Acceleration).
F is Force to be applied by Aimee = \[m\text{ }\times \text{ }a\]
= \[2\text{ }Kg\]× \[8\text{ }m/{{s}^{2}}\]= \[16\text{ }Kgm/{{s}^{2}}\]= \[16\] N.
3. To accelerate a 1000-kilogram truck at 4.00 m/s2, how much net force is required?
Ans.
Given:
a = \[4.00\text{ }m/{{s}^{2}}~\]
m =\[1000\text{ }kg\],
Therefore,
F = ma
=\[1000\times 4\]
= \[4000\]N.
Summary
Force is defined as an external cause that changes or tends to change the state of the body once applied; if the body is in motion, it comes to rest, and if at rest, then it will come to motion. It can also cause a change in the direction, shape, size, etc., of the body. It might be deduced that when the direction of force is in the direction of motion, the speed of the object rises; when it is in opposition to the direction of motion, the speed of the object decreases. Moreover, force does not necessarily have to modify the condition of motion.
FAQs on What Is Meant by Force?
1. What is meant by force in Physics?
In Physics, a force is defined as an external agent, specifically a push or a pull, that occurs when two objects interact. When applied, a force can change or attempt to change an object's state of rest or of uniform motion. It can also alter an object's shape, size, or direction. Because force has both magnitude (strength) and direction, it is classified as a vector quantity.
2. What is the formula for calculating force and what are its standard units?
The formula to calculate force is derived from Newton's Second Law of Motion. It is expressed as:
F = m × a
Where:
- F is the net force applied.
- m is the mass of the object.
- a is the acceleration of the object.
3. What are the main effects a force can have on an object?
A force can produce several distinct effects on an object. The primary effects are:
- Change the state of motion: It can make a stationary object move or stop a moving object.
- Change the speed: It can increase or decrease the speed of a moving object. For instance, pushing a swing makes it go faster.
- Change the direction of motion: It can alter the path of a moving object. For example, a batsman hitting a cricket ball changes its direction.
- Change the shape or size: It can deform an object by stretching, compressing, or bending it, like squeezing a sponge.
4. What are the two main types of forces, with examples?
Forces are broadly categorised into two main types based on whether the objects are in physical contact:
- Contact Forces: These forces act only when objects are in direct physical touch. Examples include frictional force (opposing motion between surfaces), muscular force (lifting a book), and normal force (a table supporting a book).
- Non-Contact Forces: These forces act on an object from a distance without any direct contact. Examples include gravitational force (the Earth pulling an apple down), magnetic force (a magnet attracting iron filings), and electrostatic force (a charged comb lifting paper bits).
5. Why is force considered a vector quantity and not a scalar one?
Force is considered a vector quantity because its effect depends on both its magnitude (strength) and its direction. A scalar quantity, like mass or temperature, only has magnitude. For example, pushing a door with 10 N of force on its handle will open it, but applying the same 10 N force to its hinges will have no effect on its rotation. The direction of application is crucial, which is why force must be described as a vector.
6. How do balanced and unbalanced forces differ in their effect on an object?
The key difference lies in their impact on an object's state of motion.
- Balanced forces are equal in magnitude and opposite in direction. They do not cause a change in the object's motion. If the object is at rest, it stays at rest; if it is moving, it continues to move at a constant velocity. A book resting on a table is an example, where gravity and the table's normal force are balanced.
- Unbalanced forces are unequal, resulting in a net force that is not zero. These forces always cause a change in the object's motion, meaning they produce an acceleration (a change in speed or direction). Pushing a cart from rest is an example of applying an unbalanced force.
7. Can an object be in motion even if the net force acting on it is zero?
Yes, an object can be in motion even if the net force acting on it is zero. According to Newton's First Law of Motion, a zero net force means there is no acceleration. This implies the object's velocity is constant. Therefore, an object will continue to move at a constant speed in a straight line if the forces acting on it are balanced (net force is zero). For example, a car moving at a steady 60 km/h on a straight highway has a net force of zero, as the engine's thrust is perfectly balanced by air resistance and friction.
