A sewing machine needle moves up and down in simple harmonic motion with an amplitude of 1.27 cm and a frequency of 2.55 Hz. What are the (a) maximum speed and (b) maximum acceleration of the tip of the needle?
What will be an ideal response?
(a) 20.3 cm/s (b) 326 cm/s2
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Except Mercury's orbit, the rest of the planets' orbital planes are inclined by no more than _____
A) 4.6° B) 5.2° C) 6.3° D) 3.4°
A stainless steel pin fin 5-cm-long, 6-mm-OD, extends from a flat plate into a 175 m/s air stream as shown in the sketch. Estimate (a) the average heat transfer coefficient between air and the fin. (b) the temperature at the end of the fin. (c) the rate of heat flow from the fin with glycerol at 20°C flowing over the fin at 2 m/s. The plate temperature is 50°C.
GIVEN
• A stainless steel pin fin in an air stream
• Pin length (L) = 5 cm = 0.05 m
• Pin diameter (D) = 6 mm = 0.006 m
• Glycerol velocity (U?) = 2 m/s
• Glycerol temperature (T?) = 20°C
• Plate temperature (Tp) = 50°C FIND
(a) The average heat transfer coefficient ( h c) (b) The temperature of the end of the fin (TL) (c) The rate of heat flow from the fin (qf) ASSUMPTIONS
• Steady state
• Turbulence in the glycerol approaching the fin is low
• Radiative heat transfer is negligible
• Steel is type 304
• Steel properties are uniform
• Variation of the thermal properties of glycerol and steel with temperature is negligible
PROPERTIES AND CONSTANTS
Thermal conductivity (k) = 0.285 W/(m K) Kinematic viscosity (?) = 1175 × 10–6 m2/s Prandtl number (Pr) = 12,609 for type 304 stainless steel ks = 14.4 W/(m K) at 20°C
A series LRC circuit consists of a 12.0-mH inductor, a 15.0-µF capacitor, a resistor, and a 110-V (rms) ac voltage source. If the impedance of this circuit is 45.0 ? at resonance, what is its impedance at a frequency twice the resonance frequency?
What will be an ideal response?
A rocket obeys the principles of recoil. However, it is much more difficult to apply Newton's second law to a rocket because
A. there is actually sideways momentum, because a rocket motor is just a well-controlled explosion. B. the rocket pushes against air but the air is a fluid. C. Newton's three laws do not apply in outer space. D. as the rocket motor fires the total mass of the rocket changes.