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(a) What is the peak value of a sinusoidal alternating current of 4.78 r.m.s. amperes ?
angle of 90 degrees to the horizontal as shown below. At that time they were testing
the “new” SEC450 model that has a track width of 1.5m and its center of gravity
lies midway between the wheels. The center of gravity is 0.75 meters above the
horizontal and the coefficient of friction between the tyres and the road surface is 0.7
under dry conditions.
Determine the following:
a) The maximum speed in km/h at which this car could round an unbanked
bend of 75 meters radius
b) The angle to the horizontal the driver must bank to ensure “no-side slip”
conditions at a speed of 60 km/h
c) If the driver moves up the incline to 15 degrees to the horizontal, determine
the speed at which the car in (a) above would now skid in this bend.
A 7 m diameter spherical ball is known to emit radiation at a rate of 340 W when its surface temperature is 880 K. Determine the average emissivity of the ball at this temperature. 𝜎 = 0.1714 x10-8 W/m2K 4 .
Solar radiation is incident on a flat-plate collector at a rate of 930 W/m2 . The glazing has a transmissivity of 0.82 and the absorptivity of absorber plate is 0.94. Determine the maximum efficiency of this collector.
Solar radiation is incident on a flat-plate collector at a rate of 260 W. The product of the transmissivity of glazing and the absorptivity of absorber plate is τα = 0.85 for this single glazing collector. The heat loss coefficient of the collector is 0.5 W/m2 °C. The collector is at an average temperature of 120 °C and the ambient air temperature is 67 °C. (a) Determine the efficiency of this collector. (b) Determine the efficiency of a double-glazing collector whose τα value is 0.80 and the heat loss coefficient is 0.3 W/m2 °C. Use the same collector and ambient air temperatures
If the distance between the sun and the earth was the half of what it is L = 0.5 × 1.496 ×1011 m, what would the solar constant be? The sun is a nearly spherical body that has a diameter of D = 1.393 ×109 m and the effective surface temperature of the sun is Tsun = 5778 K. 𝜎 = 5.67 x10-8 W/m2K 4 .
What changes would you notice if the sun emitted radiation at an effective temperature of 2000 K instead of 5762 K?
Solar radiation is incident on a semi-transparent body at a rate of 900 W/m2 . If 150 W/m2 of this incident radiation is reflected back and 225 W/m2 is transmitted across the body, determine the absorptivity of the body.
A 7 m diameter spherical ball is known to emit radiation at a rate of 340 W when its surface temperature is 880 K. Determine the average emissivity of the ball at this temperature. 𝜎 = 0.1714 x10-8 W/m2K 4 .
#332078 on Oct 2022