A 2.00 kg block sits at rest on level shelf and is pressed against a vertical wa

Question

A 2.00 kg block sits at rest on level shelf and is pressed against a vertical wall by a 60.0 N force that points perpendicular to the wall, as shown in the diagram below.  The coefficient of kinetic friction between the block and the wall is 0.20.  The shelf suddenly vanishes.  Calculate the force of friction exerted on the block by the wall after the disappearance of the shelf if the coefficient of static friction is (a) 0.30 and (b) 0.50. Please note that you have NOT been told whether or not the block starts sliding down the wall!  Show all work and units!

A 2.00 kg block sits at rest on level shelf and is pressed against a vertical wall by a 60.0 N force that points perpendicular to the wall, as shown in the diagram below. The coefficient of kinetic friction between the block and the wall is 0.20. The shelf suddenly vanishes. Calculate the force of friction exerted on the block by the wall after the disappearance of the shelf if the coefficient of static friction is (a) 0.30 and (b) 0.50.

Explanation / Answer

a)

weight of block = mg = 2*9.81 = 19.62 N

frictional force = N*mu

here F is normal force so,

N*mu = F*mu

so, static friction =F*mu-s = 60*0.30 = 18 N

as static friction is less than gravity block will slide down and frictional force on block will be kinetic friction

so,

force of friction = fk = F*mu-k = 60*0.20 = 12 N

b)

fs = F*mu-s = 60*0.50 = 30 N

as static friction is larger than gravity, block won't move and frictional force on block will be static friction

so,

force of friction = fs = 30 N

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.