A block with springs and friction

AI Thread Summary
The discussion centers on a physics problem involving a 5kg block attached to a spring with a spring constant of 200N/m, stretched by 10 cm. The force exerted by the spring is calculated as 20N using the formula F = -kx. To determine the maximum external force that can be applied while keeping the block at rest, the normal force is calculated as 29.05N, leading to a frictional force of 17.43N. Participants confirm the calculations and clarify that the spring is vertical, affecting the normal force and friction. The consensus is that the calculations appear correct, with emphasis on the importance of subtracting the spring force from the gravitational force to find the accurate normal force.
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Homework Statement


A block of mass 5kg is attached to a spring with a spring constant, k = 200N/m, and hangs down so that it rests on a table as shown below.(Sorry no picture) This causes the spring to strech by 10 cm from its equilibrium length. Assume the static coefficient of friction between the table and block is 0.6. An external force, F, is applied in the positive x-direction, as shown.

b. calculate the force on the block due to the stretched spring.
d. Calculate maximum force,F, that canbe applied to the block such that the block will continue to remain at rest.

Homework Equations


F=-kx
Ff=\mu*Fn


The Attempt at a Solution


b. F=-kx
F=-200N/m * .1m
F=20N

d.5kg*9.81m/s^2 - 20N = 29.05N
Ff=\mu*Fn
Ff=.6*29.05N
Ff=17.43N
 
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Is it hanging by the spring vertically? and if so I assume the .1m is the displacement from equilibrium position. In which case your answer is seeming correct. the normal determines friction which is W-T (treating spring as a tension force naturally) So your answer should be correct, assuming I understand the question. Do you know if it is wrong or right?
 
Mthees08 said:
Is it hanging by the spring vertically? and if so I assume the .1m is the displacement from equilibrium position. In which case your answer is seeming correct. the normal determines friction which is W-T (treating spring as a tension force naturally) So your answer should be correct, assuming I understand the question. Do you know if it is wrong or right?

The string is vertical and i don't have the answer which is why I'm trying to see if it's right.
 
Your answer, to the best of my knowledge is correct. You properly found the normal and friction is based on the normal. So you are correct
 
I believe this is correct. My only concern that really jumped out at me was that the force due to the spring needed to be subtracted from m*g (force due to gravity) to give a correct value for the normal force.
 

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