This experiment uses two important pieces of Physics:
Work Done (Joules J) = Force (Newtons N) x Distance moved in direction
of force (m)
Work done is the
energy required to apply a force to move something a distance. As with all
energy, it is measured in Joules (J)
Power (Watts W) = Work done/time taken (s)
Power (measured in
Watts) is how quickly work is done. It is sometimes called the rate of energy transfer.
You need to learn and remember both of these equations
The Experiment
Part 1 – Measuring
how much energy it takes to lift a mass (calculating the Work done)
You will be lifting a 1kg mass (or more/less if you wish)
from the lowest point your arm can reach (when it is straight by your side) to
the point where the mass is touching your shoulder.
If you lift the mass this distance then you are pushing the
mass upwards with a force equal to its weight and moving it a distance equal in
length to your arm.
Measure the length of your arm from the centre of your palm to your shoulder and write this length IN METRES.
The weight of the mass is the force with which the earth is
pulling the mass down to the ground with and this is the same as the force you
are pushing up on the mass with in order to lift it.
We calculate this force by
multiplying the mass in kg by the gravitational
field strength. On earth the gravitational field strength is 10 N/kg.
The energy you’ve used to lift the mass is the work done:
Work done = Force x Distance moved in direction of force
=
J
(should be between 5J and 15J)
Part 2 – Calculating
the Power of your bicep in Watts
Working in pairs, you need to count how many times you can
lift the mass in 30 seconds. Do this as fast as you can making sure you are
lifting the mass through the full height each lift. Have your partner measure
the time, count and check you are doing the exercise correctly.
Number of lifts in 30 seconds =
Total Energy used = Work done for one lift (what you
calculated above) x number of lifts
Power = Work done/time = Total energy used/30 =
W
