- #1
Liam C
- 57
- 4
Homework Statement
A 5.0kg block of wood sits on a table with a string running over a pulley suspending a mass. The largest mass that can be suspended without moving the block of wood is 0.75kg.
a) Calculate the coefficient of friction in this case.
b) What type of coefficient of friction has been calculated in this case?
Homework Equations
Fg = mg
FA = ma
FN = ?
Us = coefficient of static friction
Ff = force of friction
Us = Ff / FN
The Attempt at a Solution
m1 = 5.0kg
m2 = 0.75kg
a) Fg = m1 x g
Fg = (5)(9.8)
Fg = -49N
FA = m2 x a
FA = (0.75)(9.8)
FA = 7.35N
FN = 49 - 7.35
FN = 41.65
Ff = FA
Us = Ff / FN
Us = 7.35 / 41.65
Us = 0.18
b) static
According to the answer key, the correct coefficient is 0.15. I suspect I'm calculating the normal force incorrectly, but I was never taught how to do it in this case so I am clueless. How does this applied upward force from the suspended weight affect the force of the normal?