A70 kg human body typically contains 140 g of potassium. potassium has a chemical atomic mass of 39.1 u and has three naturally occurring isotopes. one of those isotopes, 40k, is radioactive with a half-life of 1.3 billion years and a natural abundance of 0.012%. each 40k decay deposits, on average, 1.0 mev of energy into the body.

Two students, each riding bicycles, start from the same apartment building and ride to the same building on campus, but each takes a different route. the first student rides 1100 m due east and then turns due north and travels another 1430 m before arriving at the destination. the second student heads due north for 1930 m and then turns and heads directly toward the destination.at the turning point, how far is the second student from the destination?