As a body is projected to a high altitude above the earths surface, the variation of the acceleration of gravity with respect to altitude y must be taken into account. neglecting air resistance, this acceleration is determined from the formula a=− g 0 [ r 2 /(r+y ) 2 ] , where g 0 = 9.81 m/ s 2 is the constant gravitational acceleration at sea level, r = 6356 km is the radius of the earth, and the positive direction is measured upward. with what velocity does the particle strike the earth if it is released from rest at an altitude y0 = 800 km?

Along 8-cm diameter steam pipe whose external surface temperature is 900c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 500c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 100c. a) the length of the tube for an exit temperature of the air to be 40 0c. b)the rate of heat transfer from the air. c) the fan power needed to overcome the pressure drop in this section of the duct.