16 Questions
What is the formula for calculating torque?
$\tau = F \times r$
In which unit is force measured?
N
What conditions need to be verified for a body to be in mechanical equilibrium?
$\Sigma F = 0$ and $\Sigma \tau = 0$
When is the torque zero?
When the force is passing through the pivot point
What is the direction of torque determined by?
The right-hand rule
When is a body said to be static?
When its linear velocity is zero
In static equilibrium, what happens when a stable body's center of mass is directly over its base of support?
The reaction force upwards cancels the force produced by the body weight downwards.
What is the position of the center of gravity of an erect person with arms at the side?
At approximately 56% of the person’s height measured from the soles of the feet.
What do people tend to do when carrying an uneven load to shift the center of gravity back over their feet?
Bending and extending the limbs.
What problems can people who have lost an arm experience due to continuous compensatory bending of the torso?
Permanent distortion of the spine.
What restoring torque is produced due to a person's weight when calculating the force required to topple an erect person?
$F_w \times r_w$
At what point is a person standing at rigid attention pivoting around when calculating the force applied to topple them?
Point A
What is produced by the applied force by pivoting around point A when calculating the force required to topple a person?
$τ_a = F_a \times r_a$
What is required for an erect person to be on the threshold of falling when comparing torques about point A?
Magnitudes of two torques being equal
What is larger than 68.6 N, which is required to topple an erect person?
45.7 N
What should amputees wear to restore balanced weight distribution?
Artificial arm
Study Notes
Calculating Torque and Equilibrium
- The formula for calculating torque is not specified, but it is crucial in determining mechanical equilibrium.
Mechanical Equilibrium
- A body is in mechanical equilibrium when certain conditions are verified.
- These conditions are not specified, but they are essential for maintaining equilibrium.
Torque
- Torque is zero when the force is applied through the axis of rotation or when the distance from the axis of rotation is zero.
- The direction of torque is determined by the direction of the force and the position of the axis of rotation.
Static Equilibrium
- A body is said to be static when it is at rest or moving at a constant velocity.
- In static equilibrium, when a stable body's center of mass is directly over its base of support, it remains stationary.
Center of Gravity
- The center of gravity of an erect person with arms at their side is typically around the belly button.
Compensating for Uneven Loads
- When carrying an uneven load, people tend to shift their center of gravity back over their feet by adjusting their posture.
- This compensatory bending of the torso can lead to problems for people who have lost an arm.
Restoring Torque
- The weight of a person produces a restoring torque when calculating the force required to topple them.
- This restoring torque tries to return the person to their upright position.
Toppling an Erect Person
- When calculating the force required to topple a person, they pivot around their point of support, typically the ankle.
- The applied force produces a torque that tries to topple the person.
- For an erect person to be on the threshold of falling, the torque produced by the applied force must be greater than the restoring torque.
- A force larger than 68.6 N is required to topple an erect person.
- Amputees can wear prosthetics or weighted aids to restore balanced weight distribution.
Test your understanding of torque and statics with this quiz based on Chapter 2 of Biophysics by Dr. Mohaned Mohammed. Explore concepts such as the magnitude of torque, the relationship between force and torque, and the measurement of force in Newtons.
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