Angular Kinetics

Question 1

Torque =

Answer 1

Force * D(upside down T)
DT = perpendicular distance to axis of rotation (moment arm)
DT is associated with both internal and external forces

Question 2

Moment Arms of the wrist in anatomical position

Answer 2

All muscles are synergists

Question 3

What happens when you put force directly through an axis?

Answer 3

Nothing!

Question 4

Torque or moment is a vector which means…

Answer 4

Magnitude and direction
- Counterclockwise is +
- Clockwise is -

Question 5

Scapular Force Couple

Answer 5

• Upper Trapezius and Serratus Anterior
• Not a true force couple because there is translation and rotation of the scapula

Question 6

Bone pins vs surface tracking

Answer 6

Bone pins are more accurate

Question 7

GH Force Couple: Deltoid and Rotator Cuff

Answer 7

Force Coupling needed for typical shoulder function

Question 8

Explain this example

Hint: Moment Arms

Answer 8

We see a gain of distance in the moment arm of the external force thus a larger torque. As a result the internal moment arm gets larger and force generation must get greater to allow for torque to be matched. This puts more force on the disks when the box is farther out as the internal forces must become greater.

Question 9

Center of Mass - Def

Answer 9

• Point about which the mass is evenly distributed
• Sum of torques is equal to 0

Question 10

Center of Mass and Balance

Answer 10

We must be in our base of support to keep balance. We can change our center of mass by changing our base of support.

Question 11

How would changing body position alter muscle force requirements for this task?

Answer 11

We must first shift our mass in the left photo to be able to try to generate force to get up such as massive amounts of trunk flexion. In the second photo we need less trunk flexion.

Question 12

Answer 12

Keeping our lumbar spine closer to center of mass allows for less work to be required thus we won’t have pain from tight/overworked muscle

Question 13

Answer 13

Moment arm gets larger. We want to have a more force up and down so we aren’t wasting energy. We also don’t want tons of stress on the bicep with lots of flexion.

Question 14

What does this mean?

Answer 14

The farther away the external weight, the larger the moment arm. Requires internal to match and makes it more work because resistance is higher.