Mechanical final exam: Torque and levers

What is torque?

The rotary effect of a force about an axis of rotation

- Measured as the product of force and the forces moment arm

What is the formula and units of torque?

T= F*d

Units: Nm

What is the moment arm?

The perpendicular distance from the forces line of action to the axis of rotation

What direction is positive torque?

Counterclockwise

What direction is negative torque?

Clockwise

What is the net effect for torque?

Adding multiple torques together

What happens with torque within the human body?

- The product of muscle tension and muscle moment arm produces a torque at the joint it crosses

Which of the following correctly identifies the parts of a lever within the human body

- Bone is the rigid bar

- Joint is the axis of rotation

- Muscle insertion provides the point of force

- COM of the moving segment is the point of resistance

T or F: A third class lever is favorable for efficient effort force production

When muscles on opposite sides of a joint develop tension, what determines the direction of joint movement?

Net torque

T or F? A force that causes rotation acts through the pivot point

False

T or F? By convention, counterclockwise torques are considered to be positive?

True

Which of the following would be the best indicator of the relative efficiency of a lever?

Mechanical advantage of the lever

The resistance (RA) will always be longer than the force arm (FA) in what class lever?

3rd class

Third class lever systems favor which of the following?

Both speed and ROM

What part of the body increases the moment arm?

Patella

What is isometric?

No change

What is isokinetic?

Same/constant speed

What is isotonic?

Same tension

What is a lever?

A simple machine consisting of a relatively rigid bar like body that can be made to rotate about an axis of a fulcrum

- There are first, second and third class levers

What are classes of levers?

Relative locations of the applied force, the resistance, and the fulcrum (or axis of rotation) determine lever classes

What is a first class lever?

FAR

What is a second class lever?

ARF

What is a third class lever?

AFR

If you decrease a resistive torque and huge moment arm

Is easy

If resistive gets a longer moment arm= what?

More resistive torque

What is mechanical advantage?

The ratio of the moment arm of force to the moment arm of the resistance for a given lever

What is the formula for Moment arm?

MA= FA/RA

What are the difficulty scales for Moment arms?

0-1 = difficult

1= break even

>1 = easy

What lever is a triceps extension?

First class

What kind of lever are most of body movements?

3rd class levers

What is the lever for lifting heavy?

A small force can balance a larger resistance when the force arm is longer than the resistance arm

What is a lever for motion?

A force can move a resistance through a larger ROM when the force arm is shorter than the resistance arm

- Longer handle for paint brush= easier to paint and requires less motion

What is static equilibrium?

A motionless state in which there is no net force or net torque acting

- the conditions of static equilibrium

EFv=0

EFh=0

ET=0

What is true with static equilibrium?

Both static and sum of torques =0