An object with a mass of 25 kg is lying still on a surface and is compressing a horizontal spring by 5/2 m. If the spring's constant is 4 (kg)/s^2, what is the minimum value of the surface's coefficient of static friction?

2 Answers
Jan 21, 2016

I found 0.04

Explanation:

Have a look:
enter image source here

Jan 21, 2016

mu = (kx)/(mg)
mu = 2/49
mu ~~ .04

enter image source here

Explanation:

Take a look at the figure ignore d(t) we will not need it
Now put free body diagram we will have the following equations

  1. W = N
  2. F_k =kx = F_f
    Where,
    W = mg
    N = Normal force;
    F_k = spring force
    F_f = frictional force
    now F_f = muN
    But N = mg
    So, mumg = kx substitute and get
    mu = (kx)/(mg)
    mu = 2/49