help with frictional forces (1 Viewer)

[clicker]

how do i caluclate the coefficient of friction force:

i noe F (friction) = coefficent of friction x F (normal)

A block of mass 3.00kg is being pushed across a rough surface with a velocity of 5.0 ms-1
When the pushing force is removed the block comes to rest in a distance of 3.0 m.
Calculate the coefficient of friction between the block and the rough surface.

 

[KFunk]

I havn't really worked with resistive force before but I'll give it a shot. Assuming that the deceleration was constant we can use:

v²=u² + 2as to work out the deceleration (since v=0 and a is negative)

a = u²/2s = 25/6 = 4 1/6 ms^-2 apposing the motion
So the resistive force of friction acting on the block F_r= m*a

F_r= 4 1/6 ms^-2 * 3.00kg = 12.5N
the perpendcular normal force F_n= mass*gravity = 3*9.8 = 29.4N

Finally using your little equation thingo we get:

Coefficient of friction = F_r /F_n = 12.5N/29.4N = 0.42517 (I assume it doesn't have a unit?)


Anyhow, I hope that's what you were looking for.