At noon on a cloud-free summer day, sunlight intensities at the Earth’s surface are nearly always less than 940 W/m2 (0.12 hp/ft2 ). (a) At this intensity, if the solar collector and electric motor could convert 10% of the collected solar energy to mechanical power, how large a collector would be required on a tractor to supply 100 kW (134 hp) of mechanical power? (b) If the length of the collector was twice its width, what would be the dimensions of the collector?

Three point charges, two positive and one negative, each having a magnitude of 20 μc are placed at the vertices of an equilateral triangle (30 cm on a side). what is the magnitude of the electrostatic force on the negative charge

We want to calculate the total metabolic heat generated by a singing canary taking into account heat transfer by radiation, convection and exhaling air. the air temperature is 20 oc, canary’s body internal and surface temperature is 33oc, external body surface convective heat transfer coefficient is 25.2 w/m2 .k, temperature difference between the inhaled and exhaled air is 4.3 oc, the ventilation rate is 0.74 cc of air per second, specific heat of air is 1.0066 kj/kg.k and density of air is 1.16 kg/m3 . assume the canary’s body to be a cylinder with 7 cm diameter and 9 cm length, and heat exchange is from the side as well as the top and bottom of cylinder. calculate 1) the net rate of heat lost by radiation, assuming heat gained by the bird through radiation from the surroundings is 11.5 w; 2) rate of heat transferred by convection to the surrounding air; 3) rate of heat transferred in the exhaling air without considering any internal evaporation; 4) total metabolic power.

The coefficient of friction is a number that represents the resistance to sliding between two in contact with one another.