大象传媒

Work, power and efficiency - CCEAPrescribed practical: personal power

When work is done on an object, energy is transferred. Power is the amount of work done in one second. Efficiency is a measure of how much useful energy is converted.

Part of Physics (Single Science)Energy

Prescribed practical: personal power

Purpose

A guide to carrying out a practical to investigate personal power

To plan and carry out experiments to measure personal power, by measuring the time taken to climb a staircase or performing a number of step-ups to a platform.

Apparatus

1 short flight of stairs, a 50 cm rule, a stop clock, bathroom scales marked in kg.

Measuring the time taken to climb a staircase or performing a number of step-ups to a platform

Method

  1. Measure the persons mass in kg using bathroom scales.
  2. Convert it to weight using W = mg. This equals the upward force that will move up the stairs.
  3. Measure the height of 1 step using the 50 cm rule. Record in m in a suitable table. Repeat for two more steps and calculate the average height in m.
  4. Count the number of steps and record.
  5. Calculate the vertical height = number of steps x average height of 1 step.
  6. Calculate the work done = force x vertical height.
  7. Time the person running the stairs. Record in the table. After a rest repeat the experiment and calculate average time.
  8. Calculate the persons average power using: power = \(\frac{work~done}{time~taken}\)

Safety

HazardConsequenceControl measures
StepsFallThe flight of stairs should be short. Do not run up the steps too quickly. Go one step at a time.
StepsCollisionOnly one person at a time should carry out the experiment
StepsFall/CollisionWalk back down the steps and make sure nobody is running up
HazardSteps
ConsequenceFall
Control measuresThe flight of stairs should be short. Do not run up the steps too quickly. Go one step at a time.
HazardSteps
ConsequenceCollision
Control measuresOnly one person at a time should carry out the experiment
HazardSteps
ConsequenceFall/Collision
Control measuresWalk back down the steps and make sure nobody is running up