UK GCSE level age ~14-16, ~US grades 9-10 Biology revision notes re-edit 23/05/2023 [SEARCH]

Skeleton and muscles: 3. Weight lifted and force needed calculations based on the action of muscles e.g. antagonistic muscles of elbow joint

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INDEX of biology notes on the skeleton and muscles

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(3) Weight lifted and force calculations based on the action of muscles

force and moment calculations of arm elbow joint force generated by biceps and triceps calculating force needed to lift raise a weight

Some example questions (answers)

ALL based on the diagram above for the antagonistic biceps and triceps muscles of the elbow joint

Assume the gravitational field constant is 10 N/kg

Question 1

 If d1 = 0.40 m, d2 = 5 cm, using the above diagram for help, and applying the principle of moments, calculate the minimum force needed by the biceps contraction to lift a weight of 20 N.

Question 2

 If d1 = 0.36 m, d2 = 0.06 m, using the above diagram for help, and applying the principle of moments, calculate the minimum force needed by the biceps contraction to lift a mass of 3 kg.

Question 3

 If d1 = 45 cm, d2 = 5 cm, using the above diagram for help, and applying the principle of moments, calculate the minimum force needed by the biceps contraction to lift a weight of 15 N.

Question 4

 If d1 = 48 cm, d2 = 6 cm, using the above diagram for help, and applying the principle of moments, calculate the minimum force needed by the biceps contraction to lift a weight of 2 kg.

Question 5

 If d1 = 0.50 m, d2 = 0.05 m, using the above diagram for help, and applying the principle of moments, if the maximum strength of a person's biceps muscle contraction creates a force of 150 N, calculate the maximum weight the person's arm can raise and hold.

Question 6

 If d1 = 0.60 m, d2 = 0.06 m, using the above diagram for help, and applying the principle of moments, if the maximum strength of a person's biceps muscle contraction creates a force of 180 N, calculate the maximum mass the person's arm can raise and hold.

Question 7

 If d1 = 0.50 m, d2 = 0.05 m, using the above diagram for help, and applying the principle of moments, if the maximum strength of a person's biceps muscle contraction creates a force of 200 N, calculate the maximum weight the person's arm can raise and hold.

Question 8

 If d1 = 0.40 m, d2 = 0.06 m, using the above diagram for help, and applying the principle of moments, if the maximum strength of a person's biceps muscle contraction creates a force of 240 N, calculate the maximum mass the person's arm can raise and hold.

(Answers)

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Answers to the muscle force questions using the principle of moments

Remember 1 kg mass is equivalent to 10 N on the Earth's surface.

Q1 F1 x d1 = F2 x d2, convert cm to m, 20 x 0.40 = F2 x 0.05, F2 = 20 x 0.40 / 0.05 = 160 N

Q2 3 kg = 3 x 10 = 30 N, F1 x d1 = F2 x d2, convert cm to m, 30 x 0.36 = F2 x 0.06 x F2, F2 = 30 x 0.36 / 0.06 = 180 N

Q3 F1 x d1 = F2 x d2, convert cm to m, 15 x 0.45 = F2 x 0.05, F2 = 15 x 0.45 / 0.05 = 135 N

Q4 2 kg = 2 x 10 = 20 N, F1 x d1 = F2 x d2, convert cm to m, 20 x 0.48 = F2 x 0.06, F2 = 20 x 0.48 / 0.06 = 160 N

Q5 F1 x d1 = F2 x d2, F1 x 0.50 = 150 x 0.05, F1 = 150 x 0.05 / 0.50 = 15 N

Q6 F1 x d1 = F2 x d2, F1 x 0.60 = 180 x 0.06, F1 = 180 x 0.06 / 0.60 = 18 N, mass = 18 / 10 = 1.8 kg

Q7 F1 x d1 = F2 x d2, F1 x 0.50 = 200 x 0.05, F1 = 200 x 0.05 / 0.50 = 20 N

Q8 F1 x d1 = F2 x d2, F1 x 0.40 = 240 x 0.06, F1 = 240 x 0.06 / 0.40 = 36 N, mass = 36 /10 = 3.6 kg

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