An object with a mass of #8 kg# is lying still on a surface and is compressing a horizontal spring by #5/4 m#. If the spring's constant is #3 (kg)/s^2#, what is the minimum value of the surface's coefficient of static friction?

1 Answer
Dec 20, 2016

Answer:

The static coefficient must equal 0.048

Explanation:

We are looking at a case of balanced forces here. The force of the spring #F=kx# will push on the mass with a force of

#F = (3(kg)/s^2)(5/4m)# = #15/4# N

Static friction will be equal in magnitude to this, as there is no motion.

Writing the force of friction as #F_f=muF_N = mumg#

#15/4N = mu (8kg)(9.8m/s^2)#

#3.75 N = muxx78.4N#

#mu=3.75/78.4 = 0.048#