Build and refine a small energy converter

Can a hand-powered device lift a load within a material limit?

Submit: An evidence record, explanation and revision.

Related lesson: Energy Conservation

This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.

Build the idea

A hand crank or spool can transfer energy from a person to a raised load, increasing gravitational potential energy. Some input energy becomes thermal energy through interactions. A device can change force and distance requirements without creating extra energy. Output mgh alone is not efficiency unless input energy is also measured.

Evidence and model inputs

Design criteria: raise a 0.10 kg soft load by 0.30 m in at most 15 s using a cardboard frame, teacher-approved spool, string and a handle; no powered motor. Useful gravitational output is about 0.294 J using g=9.8 m/s². Input work can be estimated only if a suitable force measurement and travel distance are available.

Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.

Materials and preparation

Cardboard frame, safe spool, string, handle, soft 0.10 kg load, ruler and timer; teacher supervises construction.

Grade-level scope

Low loads, no mains electricity, sharp tools or elevated falling weights.

Do the work

1. Sketch the energy pathway from the person through the crank to the load and surroundings.
2. Build within the supplied material limits; teacher checks frame and load security.
3. Measure lifting height and time for three trials, retaining slips or stalls.
4. Change spool size or handle leverage and retest the same load.
5. Evaluate goal performance and energy pathways; calculate efficiency only if input work is actually measured.

Learner worksheet

Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.

Check your reasoning

1. What is useful output energy?
2. Does a longer handle create energy?
3. Can output divided by lifting time estimate useful power?
4. Can efficiency be inferred from output alone?

Teacher review guide

Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.

1. Builds a converter within criteria and constraints.
2. Measures repeated useful output performance.
3. Accounts for input, output and other transfers.
4. Uses evidence to improve and evaluate the design.

Sources and standard reference

• Official NGSS HS-PS3-3 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.

Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.