Question

A box of mass 14.0 kg sits on a horizontal steel ramp 4.8 m long with a coefficient of static friction of 0.40 between the ramp and the box. The end of the ramp is slowly lifted until the box begins to slide down the ramp. What angle does the ramp make with the ground when this happens?
Once the box begins to slide down the ramp, the coefficient of kinetic friction is 0.26. How fast will the box be moving once it reaches the bottom of the ramp?

Answer 1

1.
x: ma=mg•sin α –F(fr)
y: 0=-mg•cos α +N
ma=0
0= mg•sin α-μN=
= mg•sin α-μ•mg•cos α
tan α = μ =0.4
α=arctan0.4 =21°
2.
ma=mg•sin α – μ₁mg•cos α
a=g•(sin α – μ₁•cos α) =9.8(sin22°-0.26•cos22°)=…
s=v²/2a
v=sqrt(2as)=…