Profile
Settings
Refer your friends
Sign out
The term ‘work’ in regular life has a different meaning when it comes to the scientific term of work. In regular life, what we mean when we say we are working is we are doing something. It does not matter if there is a movement involved or not, we call that working. For example, Siya is preparing for her examination and is working hard to get a good score. She spends her time reading books, making notes, practising diagrams etc. While in her day-to-day life she might say that she is working, but in the language of physics, she is hardly working.
Work
In physics, if you’re reporting that work is being done, it should need to have the following two essential characteristics:
- Force should be acting on the object
- There should be a displacement
- Displacement in the direction of force
For example, you saw a pebble lying on the ground and you pushed it to move it away from the walking path. The pebble moved due to force exerted by you and hence this particular incident will be defined as work done. The reason for the same is that in this case there is a presence of both the factors that can be identified. With the application of force to move the pebbles and the displacement of pebbles, we can say that work is being done in this case.
Work is a scalar quantity as it measures only the magnitude, not the distance. Work done essentially depends on the displacement involved and not on the direction. If the object moves back to the initial position, the network calculated will be zero as the displacement covered is zero.
We define work to be the product of force and displacement.
Work done=force. displacement
W=Fs
The work done by a force acting on an object equals the magnitude of the force multiplied by the distance moved in the direction of the force. The SI unit of work is Newton metre (N m) or Joule (J). 1J refers to the work done on the object when a force of 1 N displaces an object by 1 m along the line of action of the force.
The calculated work done can be positive when the force is applied in the direction of motion, negative when the force is applied opposite to the direction of the motion and zero when the force is applied at the right angle direction to the motion.
Solved Examples for Work Done
- Given that the force of 5 N is acting on an object that displaces it by 2m in the direction of force, calculate the work done in the given scenario.
Given,
F=5N, s=2m
W=Fs=52=10J
- A boy pulls a block of wood with a force of magnitude 25N. The force produced a displacement of 15m in the block. It is given that the angle between the displacement and force is 30°. Find the work done in this case.
Given:
F=25N, s=15m, 𝛳=30°
Word done=W=Fcos𝛳*s= 25(cos30)*15=25*√3/2*15=324.76J
- Given that an object of mass 2 kg is falling on the ground from a height of 5m. Calculate the work done by the gravitational force on the object. (g=10 ms-2)
W=mgh=2510=100J
Work Done with a Constant Force
Constant Force
The constant force is defined as the uniform amount of force exerted on an object which does not change in the given period of time. The concept of constant force is important in day-to-day life as it helps in maintaining the uniform motion of the objects. In the case of stationary objects, the exertion of the constant force helps in maintaining the equilibrium. In scientific terms, the force exerted on an object for a long period of time and given that the physical conditions remain constant, the force is referred to as the constant force.
Let’s take a look at the examples for a better understanding:
- Gravity: The definition of gravity need not be explained to anyone. Gravity is the force that all the living and non-living beings existing on the earth are experiencing as the pull towards the core. The amount of pull or the gravitational force does not change over a period of time as the physical surroundings remain constant. Hence gravitational force is an excellent example of the application of constant force in real life.
- Cycling: One of the best examples of the application of constant force in real life is cycling. How do you operate a bicycle? You apply mechanical force in order to maintain the persistent speed of the cycle. This constant exertion of force in order to operate a bicycle is an example of the application of constant force.
- Pendulum: Ever seen a pendulum? The object continues being in to and fro motion unless and until an external force is applied or it exhausts its energy. In order to maintain this continuous motion, constant force must be exerted on the pendulum.
Word done by the Constant Force
The work done by the constant force is equal to the product of the magnitude of constant force applied and the direction in which the object moves.
For example, a person is lifting an object of mass 10 kg above the ground at the height of 1 m. The person exerts the force in an upward direction, opposite to the gravity and the object is being moved at a uniform velocity. By doing this action, the work is getting done upon the object.
Conclusion
The term work has a different meaning in the scientific field. In order to guarantee that work is being done, there should be evidence of force being exerted and displacement of the object. The SI unit of work done is Joules and the calculated work may be positive, negative or zero.
