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Answer:
12 mins
Explanation:
The summation of the forces in vertical direction
= Fb - Fd - w = 0 ∴ Fd = Fb - w ----- ( 1 )
Fb ( buoyant force ) = Pair * g * Vballoon ------- ( 2 )
Pair = air density , Vballoon = volume of balloon
Vballoon = , where D = 4 ∴ Vballoon = 33.51 ft^3
g = 32.2 ft/s^2
From property tables
Pair = 2.33 * 10^-3 slug/ft^3
μ ( dynamic viscosity ) = 3.8 * 10^-7 slug/ft.s
<em>Insert values into equation 2 </em>
Fb = ( 2.33 * 10^-3 ) * ( 32.2 ) *( 33.51 ) = 2.514 Ib
∴ Fd = 2.514 - 2.5 = 0.014 Ib ( equation 1 )
Assuming that flow is Laminar and RE < 1
Re = (Pair * vd) / μair -------- ( 3 )
where: Pair = 2.33 * 10^-3 slug/ft^3 , vd = ( 987 * 4 ) ft^2/s , μair = 3.8 * 10^-7 slug/ft.s
Insert values into equation 3
Re = 2.4 * 10^7 ( this means that the assumption above is wrong )
Hence we will use drag force law
Assume Cd = 0.5
Express Fd using the relation below
Fd = 1/2* Cd * Pair * AV^2
therefore V = 1.39 ft/s
Recalculate Reynold's number using v = 1.39 ft/s
Re = 34091
from the figure Cd ≈ 0.5 at Re = 34091
<u>Finally calculate the rise time ( time taken to reach an altitude of 1000 ft ) </u>
t = h/v
= 1000 / 1.39 = 719 seconds ≈ 12 mins
Answer:
MPa
T = 1536.8 N m
Explanation:
Given data:
Torque = 3.5 k N m = 3.5*10^3 N.m
Diameter D = 5 cm = 0.05 m
a) from torsional equation we have
solving for
MPa
B)
Pa
m
m
T = 1536.8 N m
Find full question attached
Answer:
(b) By including a statement that he or she is licensed by the Board for Professional Engineers and Land Surveyors immediately above the signature line in at least 12 point type on all contracts for services
Explanation:
A PE(professional engineer) licensee must show that he is licensed in order to show and ensure public safety as he is qualified for the job he is handling. The California regulations on professional engineers holds that all professional engineers must be licensed by the board of professional engineers and Land surveyors in order to operate legally as an engineer. The engineer may show licensure through the following options:
The engineer might provide statement to each client to show he is licensed which would then be signed by the client
The engineer may choose to post a wall certificate in his work premises to show he is licensed
The engineer may choose to include a statement of license in a letterhead or contract document which must be above the client's signature line and not less than 12 point type
