Week 1

 

Discussed this week were

-       General introduction to physical concepts associated with ‘energy’ and the way energy is measured and reported. 

 

Energy = the ability of a body to do work.  Measured by the amount of work a body can do.  Units = units of work.

 

Work = the product of a displacement by the force which produces that displacement

= Fx where x = displacement or distance and F = force.  Units of work = m*l*l/(t*t) = m*l2/(t2) = m*l2*t-2. (Note – all of these definitions of the units of work are identical.  If you do not understand this notation – ask MLC!!)

Joule = unit of work in MKS system = kg m2/ sec2 = a force of 1 N (newton) produces a displacement of 1 m (meter) – see below.

Erg = unit of work in cgs system.

Kilowatt hour = unit of work commonly used in the electrical industry

 

Force = time rate of change of momentum = mass x acceleration.  F=ma.  Force required to accelerate a body is directly proportional to the mass of the body and to the acceleration produced.  Units of force = m*l/(t*t) = m*l/(t2).

Newton = unit of force in MKS system = kg m/sec2

Dyne = unit of force in cgs system = gm cm/sec2

 

Power = the rate at which work is done; takes time into consideration = work/time.  Units of power = m*l2/t3 = m*l2*t-3

Watt = unit of power in MKS system = 1 joule per second. 

 

What is truly primary energy as far as our energy sources are concerned?

  1. Nuclear energy – powers the sun, among other things.
  2. Gravitational energy – explains why the earth is hot inside (geothermal energy).  Also required for hydropower.