In 1961, John Glenn became the first American to orbit the Earth. The altitude of his Mercury spacecraft was 100 miles (160 km) above the surface of the Earth. Determine the a) orbital velocity ofthe spacecraft. b) Determine the period of time for the Glenn's spacecraft spacecraft to orbit the Earth. Note: the radius of the Earth is 6.4 x 10 meters, the mass of the Earth is 6.0 x 10 kg and the universal gravitational constant is 6.67 x 10"N m/kg". ANS. a) 7.9 x 10' m/s, b) 5400 s E-7, P-17, 18 5-16