= 
= 
How can we figure out how much energy it takes to get an airplane up to take-off speed?
If the rate of fuel consumption is proportional to the product of (force)(speed),
the total amount of fuel burned during some period of time is proportional
to the time integral of (force)(speed).
Mathematically, we can write:
=
= is called
the work done by the force.The unit of work is the newton meter (N·m) and is called the joule (J).
Thus, we can think of power (in watts, or joules/second) as the rate
at which work (in joules) is done. This is an important point!
#1 As an exercise, use the kinematics expression v2 = vo2 + 2a(x-xo) to show that the work done by the net force is equal to:
Introducing KINETIC ENERGY
The quantity ½mv2 is called
the kinetic energy (K) of a moving object. Expressed in the basic
units, the SI unit for kinetic energy is kg·m2/s2.
Work and kinetic energy share the same unit, the joule. Work and kinetic
energy are related! The amount of work done on an object determines how
much its speed changes!