Water (cp = 4180 j/kg·k) is to be heated by solar-heated hot air (cp = 1010 j/kg·k) in a double-pipe counter-flow heat exchanger. air enters the heat exchanger at 90°c at a rate of 0.3 kg/s, while water enters at 22°c at a rate of 0.1 kg/s. the overall heat transfer coefficient based on the inner side of the tube is given as 80 w/m2·k. the length of the tube is 12 m and the internal diameter of the tube is 1.2 cm.

Distance covered, s = 8ft - 4ft = 4 ftinitial velocity, u = 34 ft/sthe acrobat is moving upwards and therefore, a = -g = -9.81 m/s^2 = 32.19 ft/s^2applying equation of motion; s = ut -1/2gt^2then,4 = 34t -1/2*32.19t^24 = 34t - 16.095t^2rearranging; -16.095t^2 + 34t - 4 = 0solving the quadratic equation; t = {-34 +/- sqrt [34^2 - 4(-16.)]}/2(-16.095) = 1.06 +/- 0.93 = 0.13 or 1.99the acrobat will take 0.13 seconds to be at 8 ft above the ground. additionally, once at the maximum height, the acrobat will move down and be at the same spot (that is height) after 1.99 seconds moving down.

You need to calculate the string in between two masses

The  moon has  insufficient gravity to retain an  atmosphere. we conclude that the moon has no atmosphere  because its gravitational field is too weak to  have  retained any  atmosphere  that it had over times comparable to the age of the solar system.