Test 3 Flashcards
a body will remain at rest or continue to move with a constant speed in a straight line unless acted upon by an outside force
Newtons 1st law
Law of acceleration
F=ma
Newtons 2nd law
a force that is causing a body to speed up
force is in the same direction
propulsive force
a force that is causing a body to slow down
force is in the opposite direction
braking force
a force does not cause an acceleration, a _______ does.
net effective force
for every force, there is an equal and opposite reaction force
Newtons 3rd law
_____ opposes motion b/w two objects in contact and will always be ______ to the contact area
Friction
parallel
what is the revised newtons 2nd law
F= mv/t
formula for impuse
force x time
______ is equal to change in momentum
Impulse
what 3 things can you do to change your ability to rotate an wheel?
- increase length of lever arm
- apply force perpendicular to rigid body
- apply larger force by using foot or leg
the turing effect of a force
Torque (T) or moment of force (M)
formula for torque
T= moment arm x force
distance from the axis of rotation to the point of force application
lever arm
perpendicular distance from the force vector to the axis of rotation
moment arm
formula for the angular equivalent of newtons 2nd law
T= moment of inertia x angular acceleration
a torque that is increasing the speed of rotation
propulsive torque
a torque that is decreasing the speed of rotation
braking torque
a rigid body that is used in conjunction with a pivot point to multiply the force or speed applied to another body
lever
what are the functions of a simple machine (lever)
- balance 2 or more forces
- change direction of the applied force
- favor speed and ROM
- favor force production
FAR or RAF
1st class lever
ARF OR FRA
2nd class lever
AFR or RFA
3rd class lever
lever that can do all four functions
1st class lever
favors speed and ROM
3rd class lever
favors force production
2nd class lever
Resistance lever arm is always longer
3rd class lever
force moment arm is always longer
2nd class
examples of 1st class levers in body
neck extension
elbow extension
examples of 2nd class levers in body
push up
toe raises
examples of 3rd class levers
elbow flexion
knee extend and flex
shoulder extend and flex
hip extend and flex
most common type of lever in the body
3rd class
two forces that are equal in magnitude, opposite in direction, and in the same plane
produce pure rotation with no translation
force couple
angular impulse formula
impulse = torque x time
angular impulse is equal to ______
angular momentum (H)
To improve performance, we would want to ____________
maximize angular velocity
to minimize injury risk, we would want to __________
decrease average torque
a resistance that increases with the amount of force or torque applied
accommodating resistance
Isokinetic dynamometers maintains constant _______ no matter the torque
angular velocity
a special case where both the linear and angular accelerations are zero, and thus the sum of the external forces and sum of the external torques are zero
static equilibrium
regardless of stance, the ______ cannot be located outside the _______ to maintain balance
COP
BOS
the state of matter that makes things change, or has the potential to make things change
energy
the energy that a body has due to its motion
kinetic energy
the energy a body has that has the potential to change something but is not currently changing anything
potential energy
formula for kinetic energy
KE= 1/2 mv squared
the potential energy that a body has due to its position
gravitational potential energy
the energy a body has due to its deformatin
strain potential energy
the process of changing the amount of energy in a system
work
formula for work
w= F x d
_____ work means that the energy is entering the system
postive
______ work means that the energy is leaving the system
negative
to jump high you need to _____ your legs as much as possible at take off to increase ______ and increase _____
extend
change in position
potential energy
at the top of a jump (apex), ________ = 0
kinetic energy
as you go down, ______ energy is changed to ______ energy
potential energy is changed to kinetic energy
the amount of mechanical energy that can be expended with a given amount of energy
efficiency
the amount of energy required to perform a certain amount of work (MEE)
economy
lower energy requirement for the same amount of work =
more economical movement
- the time rate of doing work
- how energy is leaving the system
- how much force can be produced while moving quickly
power
formula for power
power= work/ time (W)
a collision where two objects bounce off each other without deformation or loss of heat
elastic collision
examples of elastic collisions
colliding pennies, billiard balls
a collision in which two objects stick together after they collide
inelastic collision
example of inelastic collisions
football players colliding
kinetic energy is conserved in a _______ collision
elastic
Kinetic energy is not conserved in a ________ collision
inelastic
the measure of elasticity of a collision between two objects
the coefficient of restitution (e)
perfectly elastic collision
e= 1
perfectly inelastic collision
e= 0
the portion of a body’s mass that is involved with a collision
effective mass
