Lecture 12- Free Body Diagrams & Forces in Human Movement

Question 1

What is the purpose of a free body diagram?

Answer 1

It is a pictorial representation of the left side of Newton’s 2nd law, focusing on the sum of forces acting on a system.

F =m*a

Question 2

What are the steps to develop a free body diagram?

Answer 2

1. Identify the system of interest.
2. Redraw as a stick figure.
3. Draw the weight force.
4. Replace external contacts with forces.
5. Show reference frame.

Question 3

How do rope-like structures behave in human movement?

Answer 3

Rope-like structures, such as muscles and ligaments, can only pull; they cannot push. The direction of force follows the structure.

Question 4

What forces act when there’s contact with a rough surface?

Answer 4

Two forces act: one along the surface due to friction and another perpendicular (normal force) to the surface, acting at the centre of pressure.

Question 5

How is free rotation around an axle represented in a free body diagram?

Answer 5

The axle is replaced by a force in any direction, either pushing or pulling, acting at the centre of rotation.

Question 6

What is represented in a free body diagram for constrained rotation around an axle?

Answer 6

The axle is replaced by both a force in any direction and a torque, either clockwise or counter-clockwise, acting at the centre of rotation.

Question 7

How are forces represented when moving through a fluid?

Answer 7

The direction depends on the velocity relationship between the flow and the system, with forces like drag and lift being examples.