Which of the following was a belief of Copernicus?
A) Earth rotated on its axis.
B) Earth was at the center of the Universe.
C) The Sun revolved around Earth.
D) Earth revolved around the Moon.
A
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An electrostatic precipitator uses an electric field to remove smoke from the air
a. True b. False Indicate whether the statement is true or false
A mass on a spring vibrates in simple harmonic motion at a frequency of 4.0 Hz and an amplitude of 5.0 cm. If a timer is started when its displacement is a maximum (hence x = 5 cm when t = 0), what is the acceleration magnitude when t = 3 s?
a. 31.6 m/s2 c. 10.5 m/s2 b. 15.8 m/s2 d. zero
A uniform rod (mass = 2.0 kg, length = 0.60 m) is free to rotate about a frictionless pivot at one end. The rod is released from rest in the horizontal position. What is the magnitude of the angular acceleration of the rod at the instant it is 60° below the horizontal?
a. 15 rad/s2 b. 12 rad/s2 c. 18 rad/s2 d. 29 rad/s2 e. 23 rad/s2
In an experimental setup in a laboratory, a long cylinder with 5-m diameter, and an electrical resistance heater inside its entire length is cooled with water flowing crosswise over the cylinder at 25oC and a velocity of 0.8 m/s. For these flow conditions, 20 KW/m of power is required to maintain a uniform temperature of 95oC at the surface of the cylinder. When water is not available, air at 25oC is used with the velocity of 10 m/s to maintain the same surface temperature. However, in this case, the cylinder surface heat dissipation rate is reduced to 400 W/m. Calculate the convection heat transfer coefficients for both water and air, and comment on the reason for differences in the value.
GIVEN • A long cylinder with diameter d=5 cm=0.05 m Case A • Crosswise water flow at 25oC and velocity of 0.8 m/s • Power required(qc/L)=20,000 W/m • Surface temperature(Ts)=95 oC Case B • Crosswise air flow at 25oC and velocity of 10 m/s • Power required(qc/L)=400 W/m • Surface temperature(Ts)=95 oC FIND • Convection heat transfer coefficient for both air and water. • Comment on differences in the values. ASSUMPTIONS • The system is in steady state