Net force acting on a piston shaft of an actuator

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Homework Help Overview

The problem involves a cylindrical piston shaft within an actuator, where compressed air exerts an upward force while friction acts against the motion. The original poster seeks to calculate the speed of the piston as it ejects from the actuator, given specific parameters such as weight, applied force, and coefficient of friction.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of net force, questioning the method for determining frictional force and the normal force. There is uncertainty about the adequacy of provided information, particularly regarding the actuator's length and how it affects calculations.

Discussion Status

The discussion is ongoing, with participants exploring the implications of missing information and questioning the relevance of the coefficient of friction without a clear method to determine the normal force. Some guidance has been offered regarding the measurement of frictional force through direct experimentation.

Contextual Notes

Participants note the lack of sufficient information to proceed with calculations, specifically the need for the normal force to utilize the coefficient of friction effectively. The length of the actuator has been provided, but further details may still be required.

rajdeep1
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Homework Statement


A cylindrical piston shaft weighs 250 g and is held vertically inside an actuator (We can assume actuator is a box with hollow cylindrical space to fit the piston shaft). Compressed air at 100 psi is supplied at the bottom of the actuator and is acting on the piston upwards with a force of 90 N. The coefficient of friction between the piston shaft and the inside wall of the actuator is 0.61. I need to calculate the speed by which the shaft will eject and shoot upwards from the actuator.

Homework Equations


Net Force= ma
d= ui*t+ 0.5*a*t^2

The Attempt at a Solution


Net Force= 90N- 0.25*9.81 - Ff (I am not sure if this is the right way to calculate the net force. Also, not sure how to calculate the frictional force here, although I do know Ff= coeff* R)

Assuming I have a net force, I can easily find the acceleration and the distance it travels in a second.

Thank you so much.
 
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Is this a textbook question or a lab? There is not enough information. You will certainly need to know the length of the actuator.
The coefficient of friction doesn't help with no way to determine the normal force.
 
It is not a textbook question, it is more of a lab question. The length of the actuator is 10 inch.
Is there any other information that we need?
Thank you.
 
rajdeep1 said:
It is not a textbook question, it is more of a lab question. The length of the actuator is 10 inch.
Is there any other information that we need?
Thank you.
As I wrote, the coefficient of friction is no help since there is no obvious way to find the normal force between piston and cylinder. It would be more helpful simply to measure the frictional force.
 
haruspex said:
As I wrote, the coefficient of friction is no help since there is no obvious way to find the normal force between piston and cylinder. It would be more helpful simply to measure the frictional force.
Thank you. Could you please tell me the ways to measure the frictional force then?
 
rajdeep1 said:
Thank you. Could you please tell me the ways to measure the frictional force then?
By direct experiment.
 

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