Measuring forces exerted by muscles

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課程筆記

Moments and Muscles

A moment is the turning effect of a force around a point.
When a muscle pulls on a bone, it creates a moment around the joint (the pivot).
The size of the moment depends on the force exerted by the muscle and the perpendicular distance from the joint to where the force is applied.
Equation: Moment = force × distance (units: Newton metres, Nm).
Distance must be measured in metres (m) and force in Newtons (N).
To find the force exerted by a muscle, rearrange: Force = moment ÷ distance.
A Newton meter can directly measure the force applied by a muscle.

Calculating Moments

Example: A biceps curl holding a 100 N weight stationary, distance 0.5 m from elbow.
Moment = 100 N × 0.5 m = 50 Nm.
If the weight is stationary, the upward force from the biceps equals the weight (100 N) – forces are balanced.
Always write the equation, substitute values, then calculate with units.

Calculating Force from Moment

If a hamstring applies a moment of 1200 Nm at 0.6 m from the knee, force = 1200 ÷ 0.6 = 2000 N.
If a biceps applies a moment of 120 Nm at 0.5 m from the elbow, force = 120 ÷ 0.5 = 240 N.
If a triceps applies a moment of 60 Nm at 0.4 m from the elbow, force = 60 ÷ 0.4 = 150 N.
Always check units: force in N, distance in m, moment in Nm.

True or False Statements

A moment is measured by a Newton meter. False – a Newton meter measures force, not moment.
A moment depends on both force and perpendicular distance to a pivot. True.
Muscles create a moment around a joint. True.

Diagram of a biceps curl showing the pivot (elbow), force (weight), and distance.

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1.What is the unit of a moment?
Easy
- ANewton metre (Nm)
- BNewton (N)
- CMetre (m)
- DJoule (J)
2.Which of the following statements is true?
Easy
- AA moment is the turning effect of a force around a point.
- BA moment is measured directly by a Newton meter.
- CA moment is the same as force.
- DA moment is the distance from a pivot.
3.What is the unit of force?
Easy
- ANewton (N)
- BNewton metre (Nm)
- CMetre (m)
- DKilogram (kg)
4.A person holds a weight stationary. The force applied by the biceps must be equal to the weight because:
Medium
- Athe forces on the weight are balanced.
- Bthe biceps is stronger than the weight.
- Cthe moment is zero.
- Dthe distance is zero.
5.Calculate the moment produced by a 50 N force at a perpendicular distance of 0.4 m from a pivot.
Easy
- A20 Nm
- B125 Nm
- C0.008 Nm
- D50.4 Nm
6.A biceps exerts a force of 200 N at a distance of 0.3 m from the elbow. What is the moment?
Easy
- A60 Nm
- B600 Nm
- C0.0015 Nm
- D200.3 Nm
7.A hamstring applies a moment of 1200 Nm at a distance of 0.6 m from the knee. Calculate the force.
Medium
- A2000 N
- B720 N
- C200 N
- D1200.6 N
8.A biceps applies a moment of 120 Nm at a distance of 0.5 m from the elbow. Calculate the force.
Medium
- A240 N
- B60 N
- C120.5 N
- D0.00417 N

更多題目

9.A triceps applies a moment of 60 Nm at a distance of 0.4 m from the elbow. Calculate the force.
Medium
- A150 N
- B24 N
- C60.4 N
- D0.00667 N
10.A person holds a 100 N weight with the forearm horizontal. The biceps muscle inserts 0.05 m from the elbow, and the weight is 0.4 m from the elbow. What is the force exerted by the biceps?
Medium
- A800 N
- B100 N
- C12.5 N
- D500 N
11.Which of the following statements is false?
Easy
- AA moment depends on force and perpendicular distance to the pivot.
- BMuscles create a moment around a joint.
- CA moment is measured by a Newton meter.
- DThe unit of moment is the Newton metre.
12.A weight is held stationary in the hand. If the distance from the elbow to the weight is doubled, and the force exerted by the biceps remains the same, what happens to the moment about the elbow?
Medium
- AIt doubles.
- BIt halves.
- CIt stays the same.
- DIt quadruples.
13.A moment is the turning effect of a force around a point. Which of the following is the correct equation for calculating a moment?
Easy
- AMoment = force × distance
- BMoment = force ÷ distance
- CMoment = distance ÷ force
- DMoment = force + distance
14.What are the correct units for a moment?
Easy
- ANewtons (N)
- BNewton metres (Nm)
- CMetres (m)
- DNewtons per metre (N/m)
15.To directly measure the size of a force applied by a muscle, which piece of equipment could be used?
Easy
- AA ruler
- BA Newton meter
- CA balance
- DA protractor
16.In a biceps curl, a person holds a 100 N weight stationary. What is the upward force applied by the biceps?
Easy
- A50 N
- B100 N
- C200 N
- D0 N
17.A person holds a 50 N weight stationary in their hand. The distance from the elbow to the weight is 0.4 m. What is the moment of the weight about the elbow?
Easy
- A20 Nm
- B200 Nm
- C125 Nm
- D0.8 Nm
18.A person's hamstring applies a moment of 1200 Nm at a distance of 0.6 m from the knee. What is the force applied by the hamstring?
Medium
- A720 N
- B2000 N
- C200 N
- D7200 N
19.A person's biceps applies a moment of 120 Nm at a distance of 0.5 m from the elbow. What is the force applied by the biceps?
Medium
- A60 N
- B240 N
- C600 N
- D0.24 N
20.A person's triceps applies a moment of 60 Nm at a distance of 0.4 m from the elbow. What is the force applied by the triceps?
Medium
- A24 N
- B150 N
- C240 N
- D0.15 N
21.A person holds a 200 N weight with their forearm horizontal. The biceps muscle inserts 0.04 m from the elbow, and the weight is 0.35 m from the elbow. What is the force exerted by the biceps to hold the weight stationary? (Assume the forearm is weightless and the system is in equilibrium.)
Hard
- A1750 N
- B800 N
- C57 N
- D22.9 N
22.In a biceps curl, the distance from the elbow to the weight is 0.4 m. The biceps muscle inserts 0.05 m from the elbow. If the biceps exerts a force of 500 N, what is the maximum weight that can be held stationary? (Assume the forearm is weightless.)
Hard
- A62.5 N
- B4000 N
- C200 N
- D100 N
23.A student measures the moment of a weight about the elbow as 30 Nm. If the distance from the elbow to the weight is 0.25 m, what is the weight?
Medium
- A120 N
- B7.5 N
- C75 N
- D0.12 N
24.A person performs a biceps curl with a weight of 80 N. The biceps muscle inserts 0.03 m from the elbow. The weight is held at a distance of 0.3 m from the elbow. What is the moment of the weight about the elbow?
Easy
- A24 Nm
- B2.4 Nm
- C240 Nm
- D0.24 Nm
25.A student wants to measure the force exerted by their biceps muscle directly. Which piece of equipment should they use?
Easy
- AA Newton meter
- BA balance
- CA ruler
- DA protractor
26.A student performs a biceps curl holding a weight. The distance from the elbow to the weight is 0.3 m. The biceps muscle inserts 0.04 m from the elbow. If the biceps exerts a force of 400 N, what is the maximum weight that can be lifted? (Assume the system is in equilibrium.)
Hard
- A53.3 N
- B300 N
- C3000 N
- D400 N
27.In an experiment to measure the force exerted by the biceps, a student holds a 50 N weight stationary. The distance from the elbow to the weight is 0.4 m. The biceps insertion is 0.05 m from the elbow. What is the force exerted by the biceps?
Medium
- A400 N
- B50 N
- C6.25 N
- D100 N
28.A student sets up an experiment to measure the force exerted by a muscle using a spring balance. They attach the spring balance to the muscle's tendon and measure the force when the muscle contracts. Which of the following is a potential source of error in this measurement?
Medium
- AThe muscle may not be contracting at its maximum force
- BThe spring balance is not calibrated
- CThe distance from the joint is not measured
- DAll of the above
29.Which of the following is the correct equation for calculating a moment?
Easy
- AMoment = force × distance
- BMoment = force ÷ distance
- CMoment = distance ÷ force
- DMoment = force + distance
30.A person holds a 60 N weight stationary. The distance from the elbow to the weight is 0.35 m. What is the moment of the weight about the elbow?
Easy
- A21 Nm
- B171 Nm
- C60 Nm
- D0.35 Nm
31.A student investigates the relationship between the force exerted by a muscle and the angle of the joint. They measure the force at different angles. Which variable should be plotted on the y-axis of a graph?
Easy
- AForce
- BAngle
- CMoment
- DDistance
32.In an experiment to measure the force exerted by the hamstring, a student applies a moment of 1500 Nm at a distance of 0.5 m from the knee. What is the force applied by the hamstring?
Medium
- A3000 N
- B750 N
- C300 N
- D1500 N
33.A student uses a Newton meter to measure the force exerted by their biceps. They record a force of 150 N. However, they later realise that the Newton meter was not zeroed correctly and reads 10 N when no force is applied. What is the actual force exerted by the biceps?
Medium
- A140 N
- B150 N
- C160 N
- D10 N
34.Which of the following statements about moments is true?
Easy
- AA moment depends on both force and perpendicular distance to a pivot
- BA moment is measured by a Newton meter
- CMuscles create a moment around a pivot
- DAll of the above
35.A student conducts an experiment to measure the force exerted by their biceps. They hold a weight stationary and measure the distance from the elbow to the weight. They then calculate the moment. What additional measurement is needed to determine the force exerted by the biceps?
Medium
- AThe distance from the elbow to the biceps insertion
- BThe mass of the arm
- CThe angle of the elbow
- DThe speed of the movement
36.What is a moment?
Easy
- AThe turning effect of a force around a point
- BThe straight-line pull of a force
- CThe speed of a muscle contraction
- DThe distance a muscle can shorten
37.A person holds a weight stationary. Which statement about the force exerted by the biceps is correct?
Medium
- AThe biceps force is equal to the weight
- BThe biceps force is greater than the weight
- CThe biceps force is less than the weight
- DThe biceps force is not related to the weight
38.A biceps curl is performed with a weight. The distance from the elbow to the weight is 0.4 m. The biceps muscle inserts 0.05 m from the elbow. If the biceps exerts a force of 500 N, what is the moment about the elbow?
Medium
- A25 Nm
- B200 Nm
- C20 Nm
- D250 Nm
39.In an experiment to measure the force exerted by the biceps, a student holds a 50 N weight stationary. The distance from the elbow to the weight is 0.4 m. The biceps muscle inserts 0.05 m from the elbow. What is the force exerted by the biceps?
Medium
- A400 N
- B50 N
- C200 N
- D100 N
40.A student measures the moment produced by a muscle as 80 Nm. The perpendicular distance from the joint to the muscle's attachment point is 0.2 m. What is the force exerted by the muscle?
Medium
- A400 N
- B16 N
- C40 N
- D160 N
41.A moment is the turning effect of a force around a point.
Easy
True or false?
42.A moment is measured by a Newton meter.
Easy
True or false?
43.A moment depends on both the force applied and the perpendicular distance to the pivot.
Easy
True or false?
44.Muscles create a moment around a joint.
Easy
True or false?
45.Which piece of equipment can be used to directly measure the force exerted by a muscle?
Easy
- ANewton meter
- BThermometer
- CRuler
- DBalance
46.What is the unit of moment?
Easy
- ANewton metre (Nm)
- BNewton (N)
- CMetre (m)
- DJoule (J)
47.A moment of 50 Nm is produced by a force of 100 N. What is the perpendicular distance from the pivot?
Medium
- A0.5 m
- B2 m
- C5000 m
- D50 m
48.A person holds a weight stationary. The biceps exerts a force of 200 N at a perpendicular distance of 0.05 m from the elbow. The weight is 0.4 m from the elbow. What is the weight?
Medium
- A25 N
- B200 N
- C50 N
- D100 N
49.Match each term with its correct unit.
Easy
- Force
- Moment
- Distance
- Newton (N)
- Newton metre (Nm)
- Metre (m)
50.Match each quantity with its correct unit.
Easy
- Moment
- Force
- Distance
- Newton (N)
- Newton metre (Nm)
- Metre (m)
51.Calculate the moment of a 50 N weight held 0.4 m from the elbow.
Medium
52.Complete the sentence: The equation for moment is moment equals _____ times _____.
Easy
The equation for moment is moment equals ____ times ____.
53.State the rearranged equation to calculate force from moment and distance.
Easy
54.Calculate the moment of a 50 N weight held 0.4 m from the elbow.
Medium
- A20 Nm
- B18 Nm
- C22 Nm
- D24 Nm

複習筆記

## Moments and Muscle Forces - A **moment** is the turning effect of a force around a point (e.g., a joint). - When a muscle pulls on a bone, it creates a moment around the joint. - The size of a moment depends on: - The **force** applied by the muscle (in Newtons, N) - The **perpendicular distance** from the joint to where the force is applied (in metres, m) ### Key Formula - **Moment = force × distance** (units: Newton metres, Nm) - Rearranged to find force: **Force = moment ÷ distance** ### Example: Biceps Curl - A 100 N weight held stationary at 0.5 m from the elbow creates a moment of: - Moment = 100 N × 0.5 m = 50 Nm - If the weight is stationary, the force applied by the biceps equals the weight (100 N upwards) because forces are balanced. ### Calculating Muscle Force - To find the force exerted by a muscle, use: **Force = moment ÷ distance** - Example: Hamstring applies 1200 Nm at 0.6 m from knee → Force = 1200 ÷ 0.6 = 2000 N - Example: Biceps applies 120 Nm at 0.5 m from elbow → Force = 120 ÷ 0.5 = 240 N - Example: Triceps applies 60 Nm at 0.4 m from elbow → Force = 60 ÷ 0.4 = 150 N ### Measuring Force Directly - A **Newton meter** can be used to directly measure the size of a force applied by a muscle. ### True/False Check - A moment is **not** measured by a Newton meter (false); it is measured in Nm. - A moment depends on both force and perpendicular distance to a pivot (true). - Muscles create a moment around a joint (true).

Moment: The turning effect of a force around a point, calculated as force × perpendicular distance from the pivot. Measured in Newton metres (Nm).
Newton meter: A device used to directly measure the size of a force, such as the force exerted by a muscle.
Perpendicular distance: The shortest distance from the pivot (joint) to the line of action of the force, measured in metres.
Joint: The point where two bones meet, around which muscles create a moment.

字卡

What is a moment?

A moment is the turning effect of a force around a point.

What creates a moment around a joint?

When a muscle pulls on a bone, it creates a moment around the joint.

What two factors does the size of a moment depend on?

The amount of force the muscle generates and the distance from the joint to where the force is applied.

What is the equation for calculating a moment?

Moment = force × distance

What are the units of force?

Newtons (N)

What are the units of moment?

Newton metres (Nm)

How is the distance measured in the moment equation?

The perpendicular distance to the pivot, measured in metres.

Rearrange the moment equation to make force the subject.

Force = moment ÷ distance

How can you directly measure the size of a force applied by a muscle?

Using a Newton meter.

A person holds a 100 N weight stationary at a distance of 0.5 m from the elbow. What is the moment of the weight?

Moment = 100 N × 0.5 m = 50 Nm.

If a weight is held stationary, what can be said about the forces on the weight?

The forces on the weight must be balanced.

In a biceps curl holding a 100 N weight stationary, what force does the biceps apply?

The biceps applies a 100 N force upwards to hold the weight still.

True or false: A moment is measured by a Newton meter.

False. A Newton meter measures force, not moment.

True or false: A moment depends on both force and perpendicular distance to a pivot.

True.

True or false: Muscles create a moment around a joint.

True.

A hamstring applies a moment of 1200 Nm at a distance of 0.6 m from the knee. Calculate the force applied by the hamstring.

Force = 1200 Nm ÷ 0.6 m = 2000 N.

A biceps applies a moment of 120 Nm at a distance of 0.5 m from the elbow. Calculate the force applied by the biceps.

Force = 120 Nm ÷ 0.5 m = 240 N.

A triceps applies a moment of 60 Nm at a distance of 0.4 m from the elbow. Calculate the force applied by the triceps.

Force = 60 Nm ÷ 0.4 m = 150 N.

What is the pivot point when a muscle creates a moment around a joint?

The joint is the pivot point where two bones meet.

In the moment equation, what does the distance represent?

The perpendicular distance from the pivot to the line of action of the force.

If a moment is 100 Nm and the distance is 0.2 m, what is the force?

Force = 100 Nm ÷ 0.2 m = 500 N.

If a force of 50 N is applied at a distance of 0.3 m from the pivot, what is the moment?

Moment = 50 N × 0.3 m = 15 Nm.

What does the acronym 'Nm' stand for?

Newton metre, the unit of moment.

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