'work , energy and power'

This PPT prepared by student-Teacher from Thiagarajar College of Preceptors for Demo Class

1. WORK , ENERGY AND POWER S. MAHESWARI 1122119BD077 PHYSICAL SCIENCE

2. Energy →force →function Work is done How work is done

3. When force act on a body in such a way that body covers some displacement, it is called work. Work is defined as a product of force(F) and displacement(d). W= Fxd Work can be defined transfer of energy. Work is scalar quantity. SI unit of work is Joule ( J ). If force make an angle with direction of motion, then for finding work done ,the component of force will be taken, which act in the direction of motion ( F cos Ө ). W = F cos ө x d work

4. (a) when direction of force and displacement is same the work done is positive. (b) when direction of force and displacement is opposite the work done is negative. (c) when force and displacement are mutually perpendicular to each other the work done is zero. Types of work

5. Man does positive work lifting box Man does negative work lowering box. Gravity does positive work when box lowers. Gravity does negative work when box raised.

6. Angle and nature of work

7. Capability of doing work is called energy. In SI unit of energy is measured in Joule ( J ). Energy is scalar quantity. Energy

8. There are two basic kinds of energy, kinetic energy potential energy Types of energy

9. Definition: energy produced produced by a object due to its motion it called as kinetic energy (K.E.). Examples , bullet fired from a gun and water flowing from dam having kinetic energy. Kinetic energy

10. The work done by the constant force (F) for a displacement (s) in the same direction is , W=F.s --------------- (i) The constant force is given by the equation F=ma --------------- (ii) The third equation of motion is, v 2 = u 2 +2as ------------ (iii) In this case initial velocity ‘v’ and final velocity is ‘0’ i.e. V 2 = 0+2as s= v 2 /2a Eqn. (ii) and (iii) in eqn. (i), W= ma.v 2 /2a K.E = ½ mv 2 Derivation of equation for kinetic energy

11. Definition : capacity to perform work bye a body due to its position or state or condition is termed potential energy (P.E) Examples : Bullet loaded in a gun and water stored in a dam have potential energy. The P.E possessed by a body in a gravitational fields is gravitational P.E. Potential energy

12. W = F x d But F= mg for gravitational force act on object and d= h for height W = mgh i.e. W(work) = P.E. P.E = mgh Where, g- acceleration due to gravity m- mass and h- height Derivation of equation for gravitational potential energy

13. Definition : It is stored as a result of deformation of an elastic object, such as stretching spring. Elastic potential energy

14. Explanation : The force that is applied on object is stored as its elastic potential energy, which helps the object to restore its initial position. According to Hooke’s law F= kx Average force required for displacement (x) is F/2 Hence work done for displacement is, W(work) = F/2× x (i.e. F= kx ) EP= W = ½ kx 2

15. In unit time work performed is termed power. Power is a measure of how fast or slow a work is done. Power is defined as the rate of work done or energy delivered. P=W/t. ( P- Power, W- Work and t- Time) Unit of power is watt (J/s). Power is scalar quantity. Other common unit of power is horse power ( hp ). 1hp=746 watt Power