- #1
theunloved
- 43
- 1
5. A 12N horizontal force F vector pushes a block weighing 5N against a vertical wall. The coefficient of static friction between the wall and the block is .60 and the coefficient of kinetic friction is .40. Assume the block is not moving initially.
(A) will the block start moving?
(B) What is the force exerted on the block by the wall?
I draw a FBD on the block, and these are all the forces that I've found:
Take y upwards and x positive going from left to right
y direction:
-mg - fs = 0
fs = -mg = -5N
x direction
F - Fc (contact) = 0
F = Fc = 12N
Part a.
The maximum static friction that prevents the block from moving down is
fs = 0.6 * 12 = 7.2 N
since magnitude of fs > magnitude of mg, the block will not move.
Part b:
From x direction, we have F = Fc = 12N, so the force on the block from the wall is vector Fc = (-12N)i
Did I do it right ? Did I miss any forces on my FBD ?
(A) will the block start moving?
(B) What is the force exerted on the block by the wall?
I draw a FBD on the block, and these are all the forces that I've found:
Take y upwards and x positive going from left to right
y direction:
-mg - fs = 0
fs = -mg = -5N
x direction
F - Fc (contact) = 0
F = Fc = 12N
Part a.
The maximum static friction that prevents the block from moving down is
fs = 0.6 * 12 = 7.2 N
since magnitude of fs > magnitude of mg, the block will not move.
Part b:
From x direction, we have F = Fc = 12N, so the force on the block from the wall is vector Fc = (-12N)i
Did I do it right ? Did I miss any forces on my FBD ?