The diagram shows a wheelchair athlete lifting a training weight with the forearm. The elbow acts as the pivot, and the biceps muscle pulls on the radius cl...
Question 1 Report
The diagram shows a wheelchair athlete lifting a training weight with the forearm. The elbow acts as the pivot, and the biceps muscle pulls on the radius close to that pivot. A coach is comparing this arrangement with a long-handled tool, where a small movement at one end can produce a larger movement at the other end.
(a) Name the bone of the upper arm that meets the radius at the elbow. [1]
(b) Describe the movement of the forearm as the biceps contracts. [2]
(c) Explain why the biceps pulls on the bone rather than pushing it. [2]
(d) Which labelled point in Fig. 1 is the pivot? [1]
(e) Explain one advantage of placing the load far from the elbow. [2]
(f) State two changes that would make lifting the load require more muscle force. [2]
Answer Details
(a) The upper-arm bone meeting the radius at the elbow is the humerus. [1]
(b) As the biceps contracts, the forearm moves upwards and flexes, or bends, at the elbow. [2]
(c) A muscle contracts by shortening. Through its tendon it can pull on a bone, but it cannot push a bone. [2]
(d) The pivot is the elbow. [1]
(e) With the load far from the elbow, a small biceps contraction produces a larger and faster movement of the hand through a wide arc. This arrangement gives movement speed and range, although it requires more effort. [2]
(f) Lifting requires more muscle force if the mass of the load is increased and if the load is held farther from the elbow. Moving the muscle attachment closer to the elbow is another acceptable change. [2]
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