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Imagine a free cylindrical body around a pipe that is pressurized with air. How does one find the force exerted on the cylindrical free body at the moment this body becomes a projectile?

*air resistance and friction is neglible.

The current way that I find the force exerted is by measuring the distance traveled and the mass of the cylindrical projectile.

Using the Kinematics:

*Δy = 0

Δy = .5at^2+VisinƟt

Δx = 0 + VicosƟt

Collapsing above equations with simultaneous equation to solve for time. Then I solve for the initial velocity.

This initial velocity is the final velocity of when the cylindrical mass leaves the pipe.

(Vf^2 - Vi^2)/2Δx = acceleration, where Δx here is the length of the pipe.

Finally Fnet = mass * acceleration.

I am trying to figure out if it is possible to figure out the force exerted on the projectile just by being given the unit of pressure like 20psi etc. My method was to covert to psi to N per in^2, then multiply that value by the area of the pipe (with set diameter and height of rocket * 2, assuming rocket is pushed in all the way).

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  • $\begingroup$ Do you know what unit pressure is measured with? $\endgroup$
    – Jimmy360
    Commented Jun 3, 2015 at 3:23
  • $\begingroup$ @Jimmy260 psi, pounds per square inch $\endgroup$
    – Bennett Yeo
    Commented Jun 3, 2015 at 19:06

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Just remember that $1 Pa = 1\dfrac{N}{m^2}$, so you just multiply by square area to obtain force. Remember that only the pressure on the end matters because the other pressure cancels out.

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  • $\begingroup$ Once I convert pressure to newtons, then I can use (a = Fnet/m) * Δx of rocket on pipe to find the Vi of the projectile, allowing me to find the distance the rocket travels, correct (given I have the angle of projection)? $\endgroup$
    – Bennett Yeo
    Commented Jun 3, 2015 at 19:15
  • $\begingroup$ @KiroYakuza Correct $\endgroup$
    – Jimmy360
    Commented Jun 3, 2015 at 22:39

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