B an open system flow both
I had this question on a quiz, it was X.
True it was a perfect running technique
Explanation:
Problem 2.5, mixing dough.
Please note dimensional units and standard formulas for energies.
Input:
Electrical energy = VIT = 110 V * 1.5 A * 5 min. * 60 s/min = 49500 joules = 49.5 kJ
Output:
Warming of dough = mCΔT = 1 kg * 4.2 kJ/(kg*K) * 5 deg.K = 21 kJ
Dissipation of energy = remainder of input energy = (49.5-21) kJ = 28.5 kJ
Fraction of energy converted to energy of dough = 21 kJ / 49.5 kJ
= forty-two percent (to the nearest percent)
The last item, dissipation of energy could be attributed to:
1. Loss in efficiency of mixer in the form of mechanical friction, heating up due to resistance of motor circuit, etc.
2. Loss in mechanical mixing of dough due to friction between mixer paddle and dough in the form of heat, part of which stays with dough (thus heating up of dough), and the remainder heats up the dough container, loss of heat to environment, air, heat of vaporization of water content of dough, etc.
Answer:
W=-1881.6J
Explanation:
we have that the change in the mass is
by solving the differential equation and applying the initial conditions we have
by solving for c and d
d=60
c=0.75
The work needed is
W = m(t) gh
by integrating we have
hope this helps!!
