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Sports clinic

  • Key Stage 3
  • Topical

Type: Activity
Learning Strategy: Case study
Topic: Forces

When a sports climber is injured, can physics help her recover for the World Championships?

Climbers have to cope with large forces on their muscles and tendons. It helps to think of the elbow as a lever. There are two kinds: Force multipliers and movement multipliers. Which kind is the elbow, and how will this knowledge help the climber in training?

The lesson makes use of ‘SodaConstructor’ a software tool for experimenting and building structures that can move, and even race against each other.

Published: 23rd June 2008
Reviews & Comments: 0

Learning objectives

Students will:
• Describe how to make a task easier by increasing the distance between the effort and the pivot
• Identify levers in a number of household devices

Try the activity

You will need Acrobat Reader installed to open the activity sheets.

11-14 (KS3)
3.1b Forces are interactions between objects and can affect their shape and motion.

Running the activity

Slide 1 – Starter
Put the students in the role of the apprentice sports scientist. Students are learning on the job by helping Ellen, a climber with an elbow injury. This scenario could be adapted to any athlete in any sport with a similar injury. Use what is in the media at the time.

Slide 2-6 – Main activity
At the end of the activity, students will be asked to give Ellen advice on her injury and how to train. To do that, they need to know the science of levers. A series of short activities will act as a tutorial.

First remind students of previous knowledge about balancing see-saws and calculating the turning effect of a force using moments (if this has already been covered).

You can organise the 5 tutorial activities as a circus. Students spend up to 5 minutes doing each activity. Each has a slide which explains what to do:

Tutorial 1: slide 2
This is about identifying the first kind of lever, called a force multiplier.
Equipment needed: Cooking tongs, nutcracker, bottle opener

Their job is to decide which of the three machines are force multipliers and explain how they work. For this they look at the text and diagram to get the idea that a small force (a long distance from a pivot) can generate a bigger force (acting close to the pivot). The two which are force multipliers are: nutcracker and bottle opener.

Tutorial 2: slide 3
This is about identifying the second kind of lever, called a distance multiplier.
Equipment needed: Cooking tongs, pliers, tweezers

Their job is to explain how each works. They look at the text and diagram to get the idea that a small movement (close to the pivot) can generate a bigger movement (acting further the pivot). The two which are distance multipliers are: cooking tongs and tweezers.

Tutorial 3: slide 4
This is about exploring how the elbow and biceps work like a lever.
Equipment needed: ruler

Students flex their arms to feel with forefinger where the tendon meets the biceps muscle [usually a fairly well defined point that can be felt with the finger [the photo shows the technique]]. Then they bend their elbow and estimate the change in length of the muscle. The also measure the movement of the hand. From these observations they will see that their hand moves a much bigger distance then the bicep muscle. The elbow works as a distance multiplier.

Tutorial 3: slide 4
This is about a simple software modelling tool to see how a movement multiplier works.
Equipment needed: Computer.

Click the 'lever' weblink below to open the model of the lever. It uses a program called ‘SodaConstructor’

The model contains a ‘muscle’, at the flat end. When you click ‘run’, this muscle contracts and expands (in time to the wave you can see passing along). Watch how much the muscle moves compared to the two ‘legs’ at the other end (these move more). Think why (it’s because the pivot is near to the muscle end. Which type of machine is it? (movement multiplier).

Tutorial 5: slide 6
This is about exploring how the elbow and biceps work like a lever.
Equipment needed: stick 0.5-1m long

Students model the elbow lever situation with a strong stick or tube and their hands. They will feel that there is an increased force required to keep the stick from moving at the short end (when someone moves the other end).

This is why the biceps and tendon experience high forces. The arm muscle is designed for a low movement input, so that it can produce high movement output. That means that your arm can be short, and still create a large movement. If it wasn’t a movement multiplier, your arm would have to trail along the floor! The disadvantage of course, is the large force that the biceps experiences to compensate. This is what can lead to injury.

Slide 7 – helping Ellen
Students can now use their knowledge of levers and the elbow joint to advise the Sports Climber about her injury and how she needs to train. Slide 7 is a set of sentence starts for their explanation.

News links

Sodarace is the online olympics pitting human creativity against machine learning in a competition to design robots that race over 2D terrains using the Sodaconstructor virtual construction kit
Computer Science for Fun
A site from one of the developers of SodaRace, on the fun side of computer science - about people, solving puzzles, creativity, changing the future.
Tendon injury
this describes a tendon injury because of huge force needed to lift:
Rock climbing strength
This account of rockclimbing seems to explain well the huge strength needed to lift our bodies (because of the big mechanical disadvantage)
Chin-up training
One arm chin up video, a way to increase strength.

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