Dust particles are pulverized rock, which has density 2500 kg/m3. They are approximately spheres 20 ?m in diameter

Treating dust as an ideal gas, what is the root-mean-square speed (thermal speed) of a dust particle at 400°C? (The Boltzmann constant is 1.38 × 10-23 J/K.) A) 5.2 × 10-5 m/s
B) 1.7 × 10-5 m/s
C) 3.0 × 10-5 m/s
D) 7.3 × 10-5 m/s


A

Physics & Space Science

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In a single-pass counterflow heat exchanger, 1.25 kg/s of water enter at 15°C and cools 2.5 kg/s of an oil having a specific heat of 2093 J/(kg K) from 95°C to 65°C. If the overall heat transfer coefficient is 280 W/(m2 K), determine the surface area required.

GIVEN
• Water cooling oil in a single-pass counterflow heat exchanger
• Water flow rate ( m w)= 1.25 kg/s
• Oil flow rate ( m o)= 2.5 kg/s
• Oil specific heat (cpo) = 2093 J/(kg K)
• Water inlet temperature (Tw, in) = 15°C
• Oil temperature
? To, in = 95°C
? To, out = 65°C
• Overall heat transfer coefficient (U) = 280 W/(m2 K)
FIND
• The surface area (A) required
SKETCH

PROPERTIES AND CONSTANTS
the specific heat of water (cpw) = 4187 J/(kg K)

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The composition of Mercury's crust is:

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A car travels at 15 m/s for 10 s. It then speeds up with a constant acceleration of 2.0 m/s2 for 15 s. At the end of this time, what is its velocity?

A) 15 m/s B) 30 m/s C) 45 m/s D) 375 m/s

Physics & Space Science

How many moles of sugar, C12H22O11, are there in 200. grams?

A) 0.585 moles B) 68,400 moles C) 1.71 moles D) 0.684 moles

Physics & Space Science