BHK Biomechanics 1 — Questions and Answers
Question 1: Newton's second law of motion as applied to biomechanics states that:
- Every action has an equal and opposite reaction
- A body in motion stays in motion unless acted upon
- Force equals mass times acceleration (F = ma) (Correct answer)
- An object at rest stays at rest
Correct answer: Force equals mass times acceleration (F = ma)
Newton's second law (F = ma) means the force applied to a body equals its mass multiplied by the resulting acceleration.
Question 2: In biomechanics, torque is defined as:
- The linear force applied along a limb
- The force per unit area on a joint surface
- The rotational effect of a force about an axis, equal to force times moment arm (Correct answer)
- The total kinetic energy of a rotating segment
Correct answer: The rotational effect of a force about an axis, equal to force times moment arm
Torque (moment of force) = Force × perpendicular distance (moment arm) from the line of force to the axis of rotation.
Question 3: The center of mass of the human body in anatomical position is located approximately:
- At the navel level
- Just anterior to the second sacral vertebra (Correct answer)
- At the xiphoid process
- At the hip joint
Correct answer: Just anterior to the second sacral vertebra
In anatomical position, the body's center of mass is typically located just anterior to the S2 vertebra, near the pelvis.
Question 4: Which type of lever system is most common in the human body?
- First class
- Second class
- Third class (Correct answer)
- Fourth class
Correct answer: Third class
Third-class levers dominate in the body because the muscle force (effort) acts between the fulcrum (joint) and the resistance (load).
Question 5: Ground reaction force (GRF) during normal walking has a characteristic double-hump pattern. What does each hump represent?
- Heel strike and push-off forces (Correct answer)
- Left and right leg forces combined
- Vertical and horizontal components
- Stance and swing phase forces
Correct answer: Heel strike and push-off forces
The two vertical GRF peaks correspond to the loading response at heel strike and the propulsive push-off at late stance.
Question 6: Angular momentum is conserved when:
- Net linear force is zero
- Net external torque acting on a system is zero (Correct answer)
- The body's center of mass is stationary
- Gravitational force is eliminated
Correct answer: Net external torque acting on a system is zero
The conservation of angular momentum holds when no net external torque acts on a system, as seen in aerial sports maneuvers.
BHK Biomechanics 1
Newton's second law of motion as applied to biomechanics states that: