Quick answer: Work is the energy transferred when a force moves an object, found from W = F × d and measured in joules. This Physics 9-10 lab on work and power gives the aim, the equipment, the safety points, a step-by-step method, sample results and 7 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
How much power can you produce? This lab measures the time taken to climb a flight of stairs at different speeds, then calculates the work done against gravity and the power developed. It shows clearly that work depends on weight and height, while power also depends on time. It works in school or at home.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: HS-PS3-1
Aim
To measure the work done and the power developed by a student climbing a flight of stairs at different speeds.
Equipment
- A flight of stairs with a handrail
- Tape measure
- Stopwatch or phone timer
- Bathroom scales or the student’s known mass
- Calculator
Safety
Use a clear flight of stairs with a handrail and good lighting. Climb only one person at a time. Wear flat shoes with grip. Never run on wet stairs; stop if you feel dizzy or breathless.
Method
- Measure the height of one step in metres. Count the steps and calculate the total height h.
- Find the mass m of the climber in kilograms.
- Place the timer at the bottom. The climber starts at rest, climbs at a chosen speed, and the timer stops when the climber’s foot reaches the top step.
- Repeat for four speeds: slow walk, normal walk, brisk walk and a fast climb. Rest for one minute between trials.
- Calculate the work W = m × g × h and the power P = W ÷ t for each trial.
Results
Sample data: mass m = 48.0 kg; 22 steps of height 0.175 m, so h = 3.85 m; g = 9.8 N/kg.
| Trial | Time t (s) | Work W (J) | Power P (W) |
|---|---|---|---|
| Slow walk | 9.2 | 1811 | 197 |
| Normal walk | 7.8 | 1811 | 232 |
| Brisk walk | 5.6 | 1811 | 323 |
| Run | 3.9 | 1811 | 464 |
Analysis questions
Question 1 Calculate the work
Show that the work done against gravity in the climb is about 1810 J.Question 2 Calculate a power
Calculate the power for the normal walk and give your answer in watts to three significant figures.Question 3 Same work, different power
Explain why the work done is the same in every trial but the power is different.Question 4 Plot and interpret
Calculate 1 ÷ t for each trial and plot power (y-axis) against 1 ÷ t (x-axis). State what the gradient represents and its value.Question 5 Compare with a lamp
Compare the power in the run with that of a 100 W lamp. State the number of lamps it could run.Question 6 Uncertainty
The stopwatch uncertainty is ±0.3 s. Calculate the percentage uncertainty in the time for the run and say how it affects the power.Question 7 Improve the lab
Suggest two improvements, and state one assumption made about the energy transferred.
