Physics, Kinetics and Kinematics Flashcards
energy
the ability of an object to do work
potential energy
stored energy
kinetic energy
the energy of motion in an object
Force
F=m.a (newton’s 2nd law)
torque
- a rotational equivalent of force
- Rotates an object about an axis of rotation
torque is synonymous with
moment
what is the formula for torque
perpendicular force . length of lever arm. T=d/F
moment or moment of force
the tendency for a force to twist or rotate an object
internal moment
a rotational force-torque from within the body
examples of internal moment
muscles, ligaments, bony architecture
External moment
a rotational force from outside the body
Examples of external moment
ground reactive force, momentum, gravity
vector
forces associated with both magnitude and direction
motion at a joint partly depends upon
leverage
levers determine
mechanical advantage ( internal moment arm/ external moment arm)
in the 1st class lever the axis of rotation is located
between the opposing forces
an example of 1st class lever in the body
sagittal plane motion of the head is controlled muscle force and weight of the head
mechanical advantage in the 1st class lever
can be less than 1 , equal to or greater than 1
the axis of rotation in 2nd class lever is located
at one end of the bone
in the 2nd class lever the internal moment has ———leverage than the external moment
greater
example of 2nd class lever
rare in the body
mechanical advantage of second class lever
greater than 1
in the 3rd class lever the axis of rotation is located
at the end of the bone
what is the most common lever type in the musculoskeletal system
3rd class lever
3rd class lever has a mechanical advantage of
less than 1
friction
the force resisting motion of objects sliding against each other
momentum
the quantity of motion possessed by a body
linear momentum
mass. linear velocity
Rotational momentum
mass moment of inertia.angular velocity
newton 1st law
A mass is at rest until acted upon by an external force
law of inertia
a body in motion tend to stay in motion and a body at rest tends to stay at rest
inertia
resistance offered by an object to set it in motion,
moment of inertia depends on
the way the mass is distributed about the center of gravity
second law of newton
an external force will cause the body to accelerate in the direction of the force