Introduction
Calculate the work and power done to lift a 2 Liter bottle of water.
Materials
2 Liter Bottle full of water, cap on.
Meter stick or 1 meter tape.
Stopwatch or clock with sweep second hand
To Do and Notice
Lift the bottle one meter
Lift the bottle 1 meter in 1 second
What's Going On?
When you lift the bottle against gravity you are exerting a force on the bottle over the distance of one meter.
Physicists say you are doing work on the bottle.
Work done in a time interval is power.
Math Root
What is the mass, m, of a 2L bottle full of water? ( m is about 2 kg)
What is the gravitational force, F, on the bottle of water
F = mg = 2 * 10 = 20 N or 20 newtons.
where g is the acceleration of gravity 9.8 m/s^2 which we round off to 10 m/s^2
What is the work done, W, to lift the bottle a distance d = 1 meter?
W = F * d = 20 N * 1 m = 20 J or 20 joules
What is the power, P, to lift the bottle 1 meter in time t = 1 second?
P = W/t = 20J/1s = 20 W or 20 watts
Scientific Explorations by Paul Doherty |
30 May 2014 |