1. What is the difference between pound-mass (Ibm) and pound-force 2. Change the
ID: 2073633 • Letter: 1
Question
1. What is the difference between pound-mass (Ibm) and pound-force 2. Change the following to SI units: (a) 70F, (b) 20 lbf, (c) 40 Btu, (d) 3. A fluid flows through a pipe of constant circular cross-section diam- (lbf)? 50 mph (miles per hour), (e) 460 R and (f) 56 psi. eter 1.1m with a mean velocity of 50cm/s. The mass flow rate of the flow through the pipe, given by the formula mass flow rate (density) (mean velocity) (cross-sectional area), is measured to be 110 kg/s. Find the specific gravity and the specific weight of the fluid 4. Consider the following equation, where F is the drag force on a sphere of diameter D in a fluid stream of low velocity V, density , and coefficient of dynamic viscosity : 9ovaD 16 There are no units associated with the numbers. Is this equation di- mensionally homogeneous? Explain. 5. State, with reasons, if you would describe the following as closed systems or open systems: (a) A rotating lawn sprinkler, if the system is taken as everything inside the sprinkler at any instant (b) The earth and its atmosphere, ignoring things flying to or falling from outer space (spaceships, rockets, asteroids etc.) (c) A baseball (d) An open container full of water initially), being heated on a stove 6. Problem 1.22C in the book. 7. Problem 1.25C in the book.Explanation / Answer
1)
One Pound force (symbol: lbf) is the gravitational pull experienced by a body of mass 1 pound/pound mass (symbol:lbm).
1 lbf
=1lbm*32.174ft/s^2 (value of g)
=32.174 poundals (since 1pdl=1lbm*ft/s^2)
1 lbm=. 454 kg
2)
a) 70oF - 32 / 5*9 = 21.111oC or 294.261 K
b) 1 lbf = 4.44822 N
for 20 lbf = 88.9644 N
c) 1 BTU = 0.00029307 KWh
for 40 BTU = 0.011722 KWh
d) 1 mph = 1.60934 Km/h
for 50 mph = 80.4672 Km/h
e) 1 R = 0.5555 K
for 460 R = 255.556 K
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