# phisics, coefficient of static friction

• Jan 2nd 2009, 10:01 AM
14041471
phisics, coefficient of static friction
i think it involves the pythagorem theorem but not really sure how to apply it. any help would be much appreciated.

"Mass of wood block without any weight = 5.0 kg; g = 9.8 m/s2"

"It was observed that the spring scale reached a force of 24.0 N to get the block moving from rest. Calculate the coefficient of static friction between the wood block and the table."
• Jan 2nd 2009, 10:03 AM
skeeter
Quote:

Originally Posted by 14041471
i think it involves the pythagorem theorem but not really sure how to apply it. any help would be much appreciated.

"Mass of wood block without any weight = 5.0 kg; g = 9.8 m/s2"

"It was observed that the spring scale reached a force of 24.0 N to get the block moving from rest. Calculate the coefficient of static friction between the wood block and the table."

is the block on a horizontal surface?

is the applied force parallel to the surface on which the block rests?
• Jan 2nd 2009, 10:41 AM
14041471
"A block of wood is dragged across a surface by a spring scale. The scale records the force as mass is added to the top of the block."

i didnt post that part of the question in the last post. i dont know if that helps, but i dont know the awnser to your question. i was given this question to solve.
• Jan 2nd 2009, 10:55 AM
skeeter
why, then, did you mention the Pythagorean theorem?
• Jan 2nd 2009, 10:57 AM
TheMasterMind
Quote:

Originally Posted by 14041471
i think it involves the pythagorem theorem but not really sure how to apply it. any help would be much appreciated.

"Mass of wood block without any weight = 5.0 kg; g = 9.8 m/s2"

"It was observed that the spring scale reached a force of 24.0 N to get the block moving from rest. Calculate the coefficient of static friction between the wood block and the table."

i believe were talking about applied force

use the frictional force equation;

mu*m*g=mu*5.0*9.8=49mu=24=24/49=0.489

plot the values and you will see
• Jan 2nd 2009, 11:39 AM
14041471
The block is sliding (I assume at constant velocity) therefore $F_{net} = \mu R$ where $R$ is the normal reaction force.
Getting the value of $R$ is simple and you're given the value of $F_{net}$ (the reading of the spring scale). Substitute the values and solve for $\mu$.