Week 11 — Pull, Pivot, Pay: A Forearm Lever Report — Traditional alternative (no AI)

Instructors: publish this instead of the adaptive version if you prefer, and unpublish or delete the adaptive one.

Assignment 10 of the term — work the forearm lever step by step, read the biceps brachii's attachments, weigh the force-versus-speed trade-off, and explain to someone new why a bottle feels heavier at your fingertips.

This week you learned that a muscle pulls its insertion toward its origin, that muscles work in teams whose roles swap when a movement reverses, how to sort a contraction and decode a muscle's name, how a limb works as a lever, and which ten major muscles move the limbs and trunk. Week 9 gave you the joints and their movement pairs, and Week 10 showed one fiber shortening as its filaments slide; this week whole muscles pull on bones across those joints. In this assignment you work four short lever-and-count problems, interpret each one, and explain the forearm lever to someone who has never studied anatomy and physiology. This week's lecture tutorial, quiz, discussion, and A&P Lab & Inquiry practise the same ideas from other angles.

The task

This week's shared dataset is Dataset H, the forearm lever. Its numbers are illustrative: engineered by the course's discipline pack to land on clean values, not measured data. A 60 N load sits in the hand, 36 cm from the elbow, and the biceps brachii inserts 4 cm from the elbow. The lever law says effort × effort arm = load × load arm. This week also names ten major muscles: the deltoid, pectoralis major, biceps brachii, and triceps brachii in the upper limb; the rectus abdominis in the trunk; and the gluteus maximus, quadriceps femoris, hamstrings, gastrocnemius, and tibialis anterior in the lower limb.

Work these four problems, showing your arithmetic and the unit with every number:

1. In Dataset H, a 60 N load sits 36 cm from the elbow. Multiply the load by its arm: what is the load side of the lever law, in newton-centimeters?
2. In Dataset H, the load side of the lever law is 2,160 newton-centimeters and the biceps brachii inserts 4 cm from the elbow. Divide by the effort arm: what effort, in newtons, must the biceps pull?
3. In Dataset H, the biceps brachii pulls 540 N to hold a 60 N load. Divide the effort by the load: how many times the load is the effort?
4. This week's ten major muscles split into 4 in the upper limb, 1 in the trunk, and 5 in the lower limb. How many major muscles is that in all?

Beside each answer, add one brief interpretation:

• Problem 1: name the lever, the fulcrum, the effort, and the load on the forearm, and say which lever class it is and what sits in the middle.
• Problem 2: name the biceps brachii's origin and insertion, say which bone moves, and explain why the effort comes out so much larger than the load.
• Problem 3: explain the force-versus-speed trade-off, saying what the arm gives up and what it gains at the hand, and say which lever class is the body's most common design.
• Problem 4: name one opposing pair from the list, say which muscle is the agonist in each direction, and name the kind of contraction when that agonist holds a load still.

Explain it to a non-expert

A younger cousin asks, "If the biceps is so strong, why does a full water bottle feel heavier when I hold it out at my fingertips than when I hold it near my elbow?" Write a 3–5 sentence message that explains, in everyday words, that the forearm works like a lever turning at the elbow, that the biceps pulls close to the elbow while the bottle sits far out, and what the arm gains in return for pulling so hard. Name one limit, for example that Dataset H's numbers are illustrative and real arms differ, or that this message is about how muscles work and not about anyone's health or training. Put any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a friend who asks how anyone can rise onto their toes with the whole body's weight on them. Model answer: "Think of your foot as a bar that tips over a pivot near your toes. Your body's weight presses down in the middle of that bar, and a muscle pulls up at the far end. Because the weight sits between the pivot and the pull, anatomists call this a second-class lever. This is a simplified classroom picture, and it leaves out the many small bones and joints in a real foot."

Use that pattern for the message to your cousin, with your own wording and evidence.

Show your arithmetic. A reader should be able to rebuild every result you report from the numbers given, without guessing which numbers you used or which operation you chose.

Deliverables

Submit a single report containing:

• the four answers, each with the arithmetic and units shown and the brief interpretation the task names for that problem;
• your message to your cousin, explaining the forearm as a lever turning at the elbow, the biceps pulling close to the elbow, what the arm gains, and one limit; and
• a one-line restatement of the numbers you used, so your results are reproducible.

Keep it to roughly one page.

Choose how you show it. Present your report as written text, or as a recorded audio or video explanation of about three minutes with a transcript, or as a labeled sketch of the forearm lever with its fulcrum, effort, load, and both arms and a short note. Every form is graded by the same scoring criteria. Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

This version is designed to be completed without AI: do the calculations, the interpretations, and the writing yourself, without a chatbot or other AI tool. You may use a calculator or a spreadsheet for the arithmetic. Submitting AI-generated work as your own, or copying another student's work, is an integrity violation under the course policy.

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