Biceps curl
In this activity, students model a biceps curl using a lever system. The model measures the force in the biceps muscle when the forearm is carrying a mass held horizontally.
By the end of this activity, students should be able to:
describe how the arm is an example of a lever (in which the elbow is a hinge)
use a model of this hinged lever to measure the forces acting
describe the size and direction of the forces acting on this hinged lever
explain that the force produced by the biceps muscles pulling on the bone of the forearm is much greater than the load of the weight force at the hand.
Bent arm
Different classes of levers are identified by the way the joint and muscles attached to the bone are arranged.
For a Class 3 lever the load is further away from the pivot than the effort. There is no mechanical advantage because the effort is greater than the load. However this disadvantage is compensated with a larger movement. This type of lever system also gives us the advantage of a much greater speed of movement.
A bent arm is a Class 3 lever. The pivot is at the elbow and the forearm acts as the lever arm. The biceps muscle provides the effort (force) and bends the forearm against the weight of the forearm and any weight that the hand might be holding.
Download the Word file (see link below) for:
introduction/background notes
what you need
what to do.
Nature of science
Scientists often use models to make and test predictions. For this reason, the New Zealand Curriculum’s Investigating in science achievement aim asks students to carry out science investigations using a variety of approaches, including the use of models.
