Download Effects of force, motion

Effects of force, motion
Kamil Sarka
Fundamental forces
• Contact (friction, centripetal…)
• Electric
• magnetic
Drag and friction
• Friction is the rubbing between solid objects.
For instance, when you rub your hands together you will feel friction,
the force that resists motion and creates heat.
• Drag is the friction between a solid object
and a liquid or a gas.
For instance, when you sail a boat across a lake, the force that
resists the movement of the boat through the water is drag.
• Heat is generated by drag just as heat is generated by
friction.
http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm
Drag and friction
Ffr   s . FN
Friction force
Normal (perpendicular) force
Coefficient of static friction
http://jersey.uoregon.edu/vlab/friction/Friction_plugin.html
Rolling friction
Coulomb friction > rolling friction
http://webphysics.davidson.edu/faculty/dmb/PY430/Friction/rolling.html
Undamped spring
F  k  x
F
k
a  x
m
m
2
dv d x
a
 2
dt dt
d2 x
k
2
2
  m (  )
2
dt
m
Undamped spring
x  A cos(t )
A cos(t )  A cos( (t  T ))
t  2
2
1 
1
T
,f  


T 2 2
k
m
Damped oscillator
Fictitious force
is an apparent force that acts on all masses in a non-inertial frame
An additional force due to nonuniform relative motion of
two reference frames is called a pseudo-force.
Angular motion
d

dt
angular velocity
period = the time of running one circle
T
2

frequency = number of circles per second
2
d

d

angular acceleration  
 2
dt
dt

f 
2
Linear vs. angular quantities
• Angular
• Linear
• Angular velocity  [s-1]
• Velocity v [m.s-1]
• Acceleration a [m.s-2] • Angular acceleration  [s-2]
Note that
a
and

r
v

r
Centripetal force
http://regentsprep.org/Regents/physics/phys06/bcentrif/default.htm
Thank you.