Academics · Middle School · Science and engineering

Move the fulcrum.
Watch the force change.

Set up a lever, a pulley system, a ramp or a wheel and axle and see the force you need, the distance you trade for it, and why the work comes out the same. Then practice, and record real trials.

Open the labWhat you get

The machine lab

Try each machine with the sliders, work the sample problem set in Practice, and load the worked example in the Lab notebook to see three classroom trials analyzed.

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What you get

Academics · Middle SchoolFree

What you finish with
A working picture of the four basic simple machines with live numbers, ten problems with worked solutions, and a lab notebook that turns spring-scale measurements into actual and ideal mechanical advantage and efficiency, printable as a lab report.
Who it is for
Students in grades 6 to 8 studying forces, work and simple machines, the science teachers who run a simple machines lab, and homeschool families doing the lab at a kitchen table.
Format
Browser lab, practice set and lab notebook. Works on a tablet, phone or computer and from the keyboard. Print a lab report or save trials as a .csv.
Access
Free. No account and no sign-in. Trials stay in this browser; nothing is sent to Caveat.
Where it lives
The Middle School space in Caveat Academics.
Support
Questions, a correction or a request: team@caveatacademic.com.

How to use it

  1. In the Machine lab, pick a machine and move the sliders. Watch the effort, the distances and the work.
  2. Lower the efficiency to see what friction does to the force you need.
  3. Work the ten problems in Practice. Each answer shows the steps.
  4. Run the real lab with a spring scale and a ruler, record each trial in the notebook and print the report.

Open the lab

The physics in the lab

Every number on the page comes from these few relationships.

Mechanical advantage

  • Lever: effort arm ÷ load arm, each measured from the fulcrum.
  • Pulleys: the number of rope segments holding up the load. A single fixed pulley has 1: it changes the direction only.
  • Inclined plane: ramp length ÷ height, for a push along the ramp.
  • Wheel and axle: wheel radius ÷ axle radius, with the effort on the wheel.

Work and efficiency

  • Weight in newtons = mass in kilograms × 9.8 N/kg near Earth's surface.
  • Work = force × distance, in joules. With no friction, work in equals work out: less force means more distance.
  • Actual mechanical advantage = load ÷ measured effort. Efficiency = work out ÷ work in × 100%, always under 100% for a real machine.
  • The lab treats beams, ropes and pulleys as weightless; real ones add a little to the effort.

The worked example notebook: a first-class lever lifting 15 N with 5.4 N (IMA 3, AMA 2.78, efficiency 92.6%), two supporting pulley segments lifting 20 N with 11.5 N (IMA 2, AMA 1.74, 87.0%), and a 1 m ramp raised 0.25 m with a 10 N cart pulled at 3.1 N (IMA 4, AMA 3.23, 80.6%). The readings are made up but typical of a classroom lab.

Sources

  1. OpenStax, College Physics 2e, chapter 9.5, "Simple Machines": mechanical advantage of levers, pulleys, inclined planes and the wheel and axle (openstax.org).
  2. OpenStax, Physics (high school), chapter 9, "Work, Energy, and Simple Machines": work, efficiency and the ideal and actual mechanical advantage (openstax.org).
  3. NIST, CODATA and SI references: standard acceleration of gravity 9.80665 m/s², rounded to 9.8 N/kg here as school texts do.
  4. NGSS Lead States, Next Generation Science Standards, middle school physical science MS-PS2 and MS-PS3 and engineering design MS-ETS1 (nextgenscience.org).

A learning lab, not an engineering calculator. Drawings are to scale within each picture but simplified; never lift heavy loads in a home lab without an adult. Support: team@caveatacademic.com.