Rod ab is made of a mild steel that is assumed to be elastoplastic with e = 200 gpa and σy = 345 mpa. after the rod has been attached to the rigid lever cd, it is found that end c is 6 mm too high. a vertical force q is then applied at c until this point has moved to position c0 . determine the required magnitude of q and the deflection δ1 if the lever is to snap back to a horizontal position after q is removed. hint: "elastoplastic" means that rod ab is permanently deformed, and will not spring back to totally undeformed.

Q_max = 13.97 kN;      δ1 = 3.39 mm

Explanation:

(a) To calculated the required magnitude of Q, we have:

The area of the rod AB ()= (3.142*d^2)/4 = (3.142*0.009^2)/4 = 6.36*10^-5 m^2

Since the rod AB will be stretched permanently (i.e. elastoplastic).

The maximum force at rod AB is, = area of the rod AB * σY = (6.36*10^-5)*(345*10^6) = 21950.8 N

Summation () = 0, Thus:

1.1*Q_max - 0.7* = 0:       1.1*Q_max = 0.7*21950.8 = 15365.56

Therefore, Q_max = 15365.56/1.1 = 13968.69 N = 13.97 kN

(b) To estimate the deflection δ1 if the lever is to snap back to a horizontal position after Q is removed, we have:

= (21950.8*1.25)/(200*10^9 * 6.36*10^-5) = 0.00216 m

Ф = /0.7 = 0.00216/0.7 = 0.0031 m

Thus, δ1 = 1.1*0.0031 = 0.00339 m = 3.39 mm

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27