KERALA PSC / PHYSICS / WORK, ENERGY AND POWER / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

 

KERALA PSC / PHYSICS / WORK, ENERGY AND POWER / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

KERALA PSC / PHYSICS / WORK, ENERGY AND POWER / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

·      Work refers to an activity involving a force and movement in the direction of the force.

·      Work depends upon two factors (i) Force applied and (ii) distance, that the body travels in the direction of force. The unit of work is Joule.

·      Power is the rate of doing work or the rate of using energy, which are numerically the same. If you do 100 joules of work in one second (using 100 joules of energy), the power is 100 watts.

·      Unit of power is watt or Joules/sec

·      1 Horse Power = 746 watt

·      Energy is the capacity to do work

·      Unit of energy is joule

·      The energy possessed by a body, by virtue of its position is called potential energy.

P.E = mgh

m = mass     g = gravity   h = height (distance between the body and the surface)

·      Energy of a body due to its motion is called kinetic energy.

Kinetic energy = ½ mv² (m = mass, v = velocity)

·      The change in the kinetic energy of an object is equal to the net work done on the object.

·      Mechanical energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position). Objects have mechanical energy if they are in motion and/or if they are at some position relative to a zero potential energy position.

·      According to law of conservation of energy the sum of total energy remains constant.

·      Law of conservation of momentum may be defined as when no external forces act on bodies then the total momentum before impact is equal to total momentum after impact.

·      Internal energy, thermal energy, chemical energy, electrical energy, nuclear energy are different forms of energy

·      Greater is the number of turns in a spring greater will be the work done.

·      Greater is the elasticity of the spring, the greater is the spring constant. Spring constant may be defined as the force required to produce an extension of one unit in the spring

·      The law of conversation of momentum can be applied to study the motion of a rocket

·      The thrust on the rocket at any instant is equal to the product of exhaust speed of the burnt gases and the rate of combustion of fuel at that instant.

·      If the total kinetic energy of two bodies remain to be the same both after and before impact the collision is said to be perfectly elastic.

·      The escape velocity from the planet, Jupiter is 61 km/second. For Mercury it is 42 km/second.

·      According to law of conservation of energy of Albert Einstein, energy can neither be created nor be destroyed but it may be transformed from one form to another.

·      The energy possessed by the water collected in the reservoir of a dam is potential energy

·      The work done by a force on a body is defined as the product of the magnitude of the force and the distance moved in the direction of force.

·      Work done = force × distance

·      A boy, swinging a stone, tied to a string, with a uniform speed in a circle in a horizontal plane over his head, does no work.

·      Unit of work is Newton metre (Nm)

 

KERALA PSC / PHYSICS / WORK, ENERGY AND POWER / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES