Work:-
In physics a force is said to do work if, when acting, there is a displacement of the point of application in the direction of the force. For example, when a ball is held above the ground and then dropped, the work done on the ball as it falls is equal to the weight of the ball (a force) multiplied by the distance to the ground (a displacement).
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Common symbols
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W |
| SI Unit |
joule (J) |
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Other units
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Foot-pound-Energy |
| In SI base unit |
1 kg.m
2⋅s−2
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Derivations from
other quantities
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W = F.S
W = τ θ |
| Dimension |
M L2 T−2 |
SI Unit:-
The SI unit of work is the joule (J), which is defined as the work expended by a force of one newton through a displacement of one metre.
The dimensionally equivalent newton-metre (N⋅m) is sometimes used as the measuring unit for work, but this can be confused with the unit newton-metre, which is the measurement unit of torque. Usage of N⋅m is discouraged by the SI authority, since it can lead to confusion as to whether the quantity expressed in newton metres is a torque measurement, or a measurement of work.
Work and energy:-
The work {\displaystyle W} W done by a constant force of magnitude {\displaystyle F} Fon a point that moves a displacement {\displaystyle s}
in a straight line in the direction of the force is the product
{\displaystyle W=Fs} W= F.S.
For example, if a force of 10 newtons ({\displaystyle F} = 10 N) acts along a point that travels 2 meters ({\displaystyle s} = 2 m), then {\displaystyle W=Fs=(10\ N)(2\ m)=20\ J.}
W= Fs = 10N 2m = 20 J
ENERGY:-
Energy is the capacity of a physical system to do work. The common symbol for energy is the uppercase letter E. The standard unit is the joule, symbolized by J. One joule (1 J) is the energy resulting from the equivalent of one newton (1 N) of force acting over one metre (1 m) of displacement.
There are two main forms of energy:-
1. Potential Energy
2. Kinetic Energy
1. Potential Energy:-
Potential energy, stored energy that depends upon the relative position of various parts of a system. A spring has more potential energy when it is compressed or stretched. A steel ball has more potential energy raised above the ground than it has after falling to the Earth. In the raised position it is capable of doing more work. Potential energy is a property of a system and not of an individual body or particle; the system composed of the Earth and the raised ball, for example, has more potential energy as the two are farther separated.
2. Kinetic Energy:-
The kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.
