Kinetic friction?

Question

a box is given a push so that it slides across the floor. How far will it go, given that the coeffficient of kinetic friction is 0.19 and the push imparts an initial speed of 4.1 m/s?

Answer 1

Kinetic energy = work done to stop the box by friction
Ke=W =fs where
f- force of friction
s - distance this force was doing the work

f=uN=umg where
u -coefficient of friction
g - acceleration due to gravity

.5mV^2=umgs

s= V^2/ug =
S=(4.1)^2/( 2x0.19 x 9.81)=4.5m

Answer 2

Friction is the force of two surfaces in contact. It is not a fundamental force, as it is derived from electromagnetic forces between atoms. When contacting surfaces move relative to each other, the friction between the two objects converts kinetic energy into thermal energy, or heat. Friction between solid objects is often referred to as Dry Friction and frictional forces between two fluids (gases or liquids) as Fluid Friction. In addition to these there is also Internal Friction which illustrates a body's ability to recover from external deformation. Contrary to popular belief, sliding friction is not caused by surface roughness, but by chemical bonding between the surfaces. Surface roughness and contact area, however, do effect sliding friction for micro- and nano-scale objects where surface area forces dominate inertial forces.

Kinetic friction
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Kinetic (or dynamic) friction occurs when two objects are moving relative to each other and rub together (like a sled on the ground). The coefficient of kinetic friction is typically denoted as μk, and is usually less than the coefficient of static friction. From the mathematical point of view, however, the difference between static and kinetic friction is of minor importance: Let us have a coefficient of friction which depends on the sliding velocity and is such that its value at 0 (the static friction μs ) is the limit of the kinetic friction μk for the velocity tending to zero. Then a solution of the contact problem with such Coulomb friction solves also the problem with the original μk and any static friction greater than that limit.

Since friction is exerted in a direction that opposes movement, kinetic friction usually does negative work, typically slowing something down. There are exceptions, however, if the surface itself is under acceleration. One can see this by placing a heavy box on a rug, then pulling on the rug quickly. In this case, the box slides backwards relative to the rug, but moves forward relative to the floor. Thus, the kinetic friction between the box and rug accelerates the box in the same direction that the box moves, doing positive work.

Examples of kinetic friction:

Sliding friction is when two objects are rubbing against each other. Putting a book flat on a desk and moving it around is an example of sliding friction
Fluid friction is the friction between a solid object as it moves through a liquid or a gas. The drag of air on an airplane or of water on a swimmer are two examples of fluid friction.

Answer 3

friction, f=m*g*u
and work is f*d

KE=.5*m*v^2

these will balance


m*g*u*d=.5*m*v^2
solve for d

d=.5*v^2/(g*u)

4.5 m

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