Biomechanics of Torque and Moment Arms

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Questions and Answers

If the moment arm of Force W was increased to 15 cm, what would the new torque be?

320 N⋅cm

280 N⋅cm

200 N⋅cm

300 N⋅cm (correct)

Imagine the forearm weight is doubled. What would the new torque be if the moment arm remained at 13cm?

1040 N⋅cm

260 N⋅cm

520 N⋅cm (correct)

130 N⋅cm

If the forearm was held at a different angle, such as 45 degrees, would the moment arm of Force W need to be adjusted?

No, because the moment arm is always measured perpendicular to the line of action of the force, which remains constant regardless of the angle of the forearm.

No, because the moment arm is the distance to the center of the forearm, which remains constant regardless of the angle of the forearm.

Yes, because the moment arm is the distance to a point on the force vector, which changes with the angle of the forearm.

Yes, because the moment arm is the distance to the line of action of the force, which changes with the angle of the forearm. (correct)

What would be the torque if the forearm was rotated 90 degrees so that Force W was pointing directly towards the axis of rotation?

0 N⋅cm (A) Signup and view all the answers

If the biceps muscle was contracting, and Force B was 50N with a moment arm of 5cm, what would the net torque acting on the forearm be?

110 N⋅cm (C) Signup and view all the answers

Which of the following best explains why a larger moment arm for the biceps is advantageous in this scenario?

It increases the torque generated by the biceps, requiring less muscle force. (A) Signup and view all the answers

What is the primary reason for the possible decrease in range of motion (ROM) when the moment arm of the biceps is increased?

The insertion point of the biceps is further away from the axis of rotation, potentially limiting the joint's ability to fully extend. (A) Signup and view all the answers

What is the initial value of the moment arm for the biceps muscle before the surgical procedure?

5 cm (D) Signup and view all the answers

Which of the following equations accurately represents the force balance equation used to calculate the force required by the biceps muscle?

Force B x 6.5 cm - Force W x 13 cm - Force R x 30 cm = 0 (A) Signup and view all the answers

What is the calculated force required by the biceps muscle after the surgical procedure, to maintain equilibrium?

316.92 N (D) Signup and view all the answers

What is the net torque acting on the system?

0 N*cm (C) Signup and view all the answers

What is the magnitude of the torque created by force W?

312 N*cm (C) Signup and view all the answers

If the force W is doubled, what would be the new force exerted by the biceps?

104 N (B) Signup and view all the answers

If the distance from the pivot point to force B is increased, how would the force required from the biceps change?

Decrease (B) Signup and view all the answers

In this scenario, which of the following would be considered the 'lever arm'?

The distance from force B to the pivot point (B) Signup and view all the answers

What is the primary reason for the discrepancy between the two calculations of Force B in the provided content?

The second calculation correctly accounts for the moment arm of Force W, while the first calculation does not. (B) Signup and view all the answers

If the person were to hold a heavier object in their hand, without changing the position of their arm, how would this affect the force exerted by the biceps muscle?

The force exerted by the biceps muscle would increase to counterbalance the increased weight. (B) Signup and view all the answers

Based on the provided information, if the person were to move their hand closer to the elbow joint, reducing the moment arm for Force W, which of the following would be the most likely effect on Force B?

Force B would decrease as the moment arm of Force W decreases. (C) Signup and view all the answers

Assume that the person were to shift the position of their arm such that the distance from the elbow joint to the weight is doubled. How would this affect the force exerted by the biceps muscle to maintain equilibrium?

Force B would need to be doubled to maintain equilibrium. (A) Signup and view all the answers

If the person were to extend their arm fully, essentially straightening it, what would be the most likely impact on the system's equilibrium?

The system would become unstable, as the moment arm of Force W would drastically increase, leading to an imbalance. (D) Signup and view all the answers

If the length of the forearm was reduced while maintaining the weight and the position of the insertion point of the biceps, what would happen to the required force by the biceps?

The force required by the biceps would increase. (C) Signup and view all the answers

Assuming the weight and the moment arms remain constant, what would be the effect on the required force by the biceps if the insertion point of the biceps is moved back to its original position?

The force required by the biceps would decrease. (A) Signup and view all the answers

If the weight of the object held in the hand is doubled, what would happen to the required force by the biceps? Assume that the moment arms of all forces remain constant.

The force required by the biceps would be doubled. (A) Signup and view all the answers

A 3rd class lever is characterized by which of the following?

The resistance is applied between the force and the axis. (C) Signup and view all the answers

Which of the following accurately describes the relationship between force, resistance, and axis in a 2nd class lever?

The resistance is located between the force and the axis. (B) Signup and view all the answers

If the biceps muscle is unable to contract, and the moment arm of the forearm remains the same, to maintain equilibrium, what would need to change?

The weight must be decreased. (B) Signup and view all the answers

What would be the effect on the required force by the biceps if the weight is held at a different angle, such as 45 degrees, assuming the moment arm of the biceps remains the same?

The force required by the biceps will increase. (A) Signup and view all the answers

In a 1st class lever, the axis of rotation is located ______.

Between the force and the resistance. (D) Signup and view all the answers

If an individual is performing a bicep curl, which lever class is being utilized?

Third Class (C) Signup and view all the answers

If the weight of the object (Force R) was decreased to 130 N, and the moment arm of the biceps remained at 5 cm, what would be the new force exerted by the biceps (Force B) to maintain equilibrium?

206 N (A) Signup and view all the answers

Assume that the person is able to increase the force exerted by the biceps muscle (Force B) by 20%. What would the new moment arm for the biceps need to be in order to maintain equilibrium with the original weight (Force R = 260 N)?

4.17 cm (A) Signup and view all the answers

Which of the following is NOT a true statement about a lever system?

The force applied is always smaller than the resistance. (C) Signup and view all the answers

Imagine the forearm weight (Force W) is doubled, but the moment arm of the biceps remains at 5 cm. What new force would be required from the biceps to maintain equilibrium?

728 N (B) Signup and view all the answers

Which of these scenarios best exemplifies Newton's Third Law of Motion?

A car accelerating quickly from a stop sign, pushing against the road with its tires. (B) Signup and view all the answers

If the moment arm of Force W is increased to 15 cm, how would the force exerted by the biceps muscle (Force B) need to change to maintain equilibrium? Assume the weight (Force R) remains at 260 N.

Increase by 20% (F) Signup and view all the answers

Suppose the person is holding the weight in their hand, and the system is in equilibrium. Now, they decide to rotate their forearm, so that the angle between their forearm and the upper arm is 90 degrees. Assuming the weight (Force R) and the moment arm for the biceps remain the same, what happens to the moment arm (Force W)?

It decreases to 0 cm (D) Signup and view all the answers

In which scenario does inertia play the most significant role?

A heavy rock resting on a table, remaining motionless until someone pushes it. (D) Signup and view all the answers

Which of the following scenarios demonstrates the concept of momentum in action?

A bowling ball striking pins, transferring energy and causing them to fall. (B) Signup and view all the answers

Which of these scenarios would be most affected by the force of friction?

A hockey puck gliding across a sheet of ice. (A) Signup and view all the answers

Which of the following scenarios BEST demonstrates how Newton's Second Law of Motion applies in everyday life?

Person pushing a heavy box across a room. (C) Signup and view all the answers

Study Notes

Calculating Joint Reaction Forces in Static Equilibrium

Static equilibrium means the system is not moving
All torques applied around the elbow joint sum to 0
Torque = force x distance
Forces in opposite directions must be equal for equilibrium
Force W = weight of the forearm
Force B = force applied by the biceps
Force W is applied with a moment arm of 13 cm
Force B is applied with a moment arm of 5 cm
If the forearm weighs 20N, what is the torque applied by the weight of the forearm?
Torque = 20N x 13 cm = 260 N*cm

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Description

This quiz focuses on the principles of torque and moment arms in biomechanics, particularly regarding the forces acting on the forearm. Explore various scenarios involving changes to moment arms, angles, and forces to understand their impact on torque calculations. It's essential for students studying biomechanics and human movement.