L21 Flashcards
If surface isn’t flat, need to find:
Normal force (how much is directed straight into the box)
-create a coordinate system
How to make a coordinate system for an uneven surface
-motion of the box and friction are parallel to the slope
-project all forces onto a coordinate system where one axis is parallel to the slope and th either is perpendicular
Steps for an uneven surface finding force
Find normal force with co-sign
Find friction multiplying normal force and 0.71
A normal force vector is always perpendicular to the surface
True
Work
The product of the magnitude of the force applied to an object and the distance the object moves in the direction of applied force
Work= Force x Distance
USUALLY is
W= F x cos THETA x s (displacement)
Positive Work
The object is moved in the same direction of the force
CONCENTRIC
Negative Work
The object is moved in the opposite direction of the force
ECCENTRIC
Power
The amount of work done per unit of time (the rate of mechanical work)
-units are watts or joules
P= dW/ dt
W= work done
T=time
D= differential or derivative of
Transfer of Momentum (2)
Simultaneous kinetic chain linking -multiple muscle groups and segments at the same time
Sequential kinetic chain linking: activation of muscle groups and segments at different time throughout the movement
Energy
The capacity to do work
-light, heat, nuclear, electrical, mechanical
Two main types of mechanical energy
Kinetic: refers to the energy resulting from something in motion
Potential: refers to the capacity to do work because of position or form
Kinetic Energy
KE= 1/2 (mv squared)
-ability of a moving object to do work resulting from its motion
-measured in joules
Potential Energy
PE= (mass x gravity x height)
-energy due to an objects position (capacity to do work)
Strain energy
SE= 1/2 k x change in x squared
K= stiffness constant
Change in x= distance over which the object is deformed
