A hot-air balloon is 120 ft above the ground when a motorcycle (traveling in a straight line on a horizontal road) passes directly beneath it going 30 mi/hr (44 ft/s). if the balloon rises vertically at a rate of 8 ft/s, what is the rate of change of the distance between the motorcycle and the balloon 9 seconds later?

Which is not true about oxygen-17 and oxygen-18?

Engines for propeller-driven aircraft are limited in their maximum rotational speed by the fact that the tip speed of the propeller must not approach the speed of sound in air (mach i). taking 6 ft as a typical diameter for a propeller of a light airplane and 1100 fils as the speed of sound, find the upper limit on the rpm (revolutions per minute) of the propeller shaft.

Do you think you could give me the answers to #29?