can anyone tell about work and energy which is in 9th class physics
Answers
The work W {\displaystyle W} W done by a constant force of magnitude F {\displaystyle F} F on a point that moves a displacement s {\displaystyle s} s in a straight line in the direction of the force is the product
W = F s {\displaystyle W=Fs} {\displaystyle W=Fs}.
For example, if a force of 10 newtons ( F {\displaystyle F} F = 10 N) acts along a point that travels 2 metres ( s {\displaystyle s} s = 2 m), then W = F s = ( 10 N ) ( 2 m ) = 20 J . {\displaystyle W=Fs=(10\ N)(2\ m)=20\ J.} {\displaystyle W=Fs=(10\ N)(2\ m)=20\ J.} This is approximately the work done lifting a 1 kg object from ground level to over a person's head against the force of gravity.
The work is doubled either by lifting twice the weight the same distance or by lifting the same weight twice the distance.
Work is closely related to energy. The work-energy principle states that an increase in the kinetic energy of a rigid body is caused by an equal amount of positive work done on the body by the resultant force acting on that body. Conversely, a decrease in kinetic energy is caused by an equal amount of negative work done by the resultant force.
From Newton's second law, it can be shown that work on a free (no fields), rigid (no internal degrees of freedom) body, is equal to the change in kinetic energy K E {\displaystyle KE} KE of the linear velocity and angular velocity of that body,
W = Δ K E . {\displaystyle W=\Delta KE.} W=\Delta KE.
The work of forces generated by a potential function is known as potential energy and the forces are said to be conservative. Therefore, work on an object that is merely displaced in a conservative force field, without change in velocity or rotation, is equal to minus the change of potential energy P E {\displaystyle PE} {\displaystyle PE} of the object,
W = − Δ P E . {\displaystyle W=-\Delta PE.} W=-\Delta PE.
These formulas show that work is the energy associated with the action of a force, so work subsequently possesses the physical dimensions, and units, of energy. The work/energy principles discussed here are identical to Electric work/energy principles.
for work to be done , there are two condition
a force must applied.
the body should move in the direction of applied force or its shape or size should change.
work is also said to be done if the force acting on the body changes its position, shape, speed or direction of motion.
some examples where work is done are moving a cart , hitting a ball with a bat ,etc.
work is zero if the motion of the body is normal to force and there is no displacement.
energy is defined as the capacity of a body to do work.
the SI unit of energy is joule. in nature energy exists in different forms. like sound energy,light energy,muscular energy,electrical energy amd many more.when work is done on a body it increases the energy of the body.