,
Statics : Friction
 

[ the laws of friction ][ the angle of friction]

 

 

 

 

Friction is the force that opposes movement.

limiting friction

The 3 Laws of Friction

1.

The limiting frictional force ( FL )is directly proportional to the normal contact force ( N )

limiting friction proportional to normal reaction

note: limiting frictional force is the maximum frictional force

2.

The ratio of the limiting frictional force ( FL ) to the normal contact force ( N ) is called the coefficient of friction (μ )

coefficient of friction

3.

When there is no motion, but the object is on the point of moving,

applied force = frictional force(limiting friction)

and when there is motion,

applied force > frictional force(limiting friction)

then this equality applies:

FL = μ N

Up to this point, when the frictional force is less than limiting friction(maximum)*, then the inequality below applies.

FL< μ N

*object is static and not on the point of moving

Example #1

A flat stone is thrown horizontally across a frozen lake.
If the stone decelerates at 2.5 ms-2 , what is the coefficient of friction between the stone and the ice? (take g=10 ms-2)

friction prob #01

Example #2

A 2 kg mass in limiting equilibrium rests on a rough plane inclined at an angle of 30 deg. to the horizontal.
Show that the coefficient of friction between the mass and the plane is √3 / 3 .

inclined plane friction problem

friction prob #2

back to top

 

The Angle of Friction

angle of friction

If we examine the normal reaction force( N ) and the frictional force( FL ) when it is limiting, then the equation FL = μ N applies.

If the resultant between N and FL is R , and it is inclined at an angle α(alpha) to the normal N, then we can write equations for FL and N in terms of R .

angle of friction

In example #2(above) the angle of friction = tan -1(√3 / 3)
= tan -1(0.5773) = 30o (the angle of the plane)

 

back to top

 

your stop for the best in math, science & programming tutorials on the Net revision help to get a better result incremental success advanced physics for secondary/high school, including much in-depth content common to first year university courses your one stop for the best in math, science and programming tuition revision help for a better result incremental success advanced physics for high school/secondary and 1st year university fast-track learning for everyone

[ PURE MATHS ][ MECHANICS ][ STATISTICS ]

 

VIDEO

linear motion
acceleration
average velocity
instantaneous velocity
circular motion 1
projectile motion
parabolic motion
relative motion
Newton's 2nd Law
connected particles
KE & PE changes
power
elastic strings
conservation momtm.
coefft. restitution
 
 

INTERACTIVE

 
 

EXAM PAPERS(.pdf)

EdxlM1 Mechanics spec.
EdxlM1 Mechanics ans.
EdxlM2 Mechanics spec.
EdxlM2 Mechanics ans.
EdxlM3 Mechanics spec.
EdxlM3 Mechanics ans.
EdxlM4 Mechanics spec.
EdxlM4 Mechanics ans.
EdxlM5 Mechanics spec.
EdxlM5 Mechanics ans.
 

TOPIC NOTES(.pdf)

 
uniform acceleration
non-uniform accln.
simple harmonic motion
projectiles
circular motion
relative motion
Newton's Laws
connected particles
work & energy
power & efficiency
more circular motion
elastic strings
impulse
conservation momtm
coeff. restitution
part. forces in equilib.
friction
rigid bodies
MORE...
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Google