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Finding Applied Force from Coefficient of Friciton and mass

  • #1
So I've been stuck on this type of question, please help!!

You are pushing horizontally on a 3.0 kg box of wood, pressing against a wall. If the coefficient of static friction is 0.60, how much force must you exert on the block to prevent it from sliding down?


Homework Statement


What is the force applied to keep the box from sliding down?

m= 3.0kg
u= o.60
g=9.81


Homework Equations



FF=uFn
Fnet = ma


The Attempt at a Solution



I tried to use the equation FF=uFn:

FF = .6(3)(9.81)
FF=17.658 N


Am I doing this correct?
 

Answers and Replies

  • #2
NascentOxygen
Staff Emeritus
Science Advisor
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1,072
Hi jmcpherson82. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]


The vertical forces must balance. The upward force due to friction = 0.6 Fn
 
Last edited by a moderator:
  • #3
So how would I find Fnet without acceleration? Because then I can't do the equation Fnet = ma
 
  • #4
662
307
So how would I find Fnet without acceleration? Because then I can't do the equation Fnet = ma
Fnet=0
EDIT: Oh, N.O.'s talking about normal force not net force.
 
  • #5
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,072
So how would I find Fnet without acceleration? Because then I can't do the equation Fnet = ma
The upward force = the downward force

The upward force is due to friction.
 

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