Calculate the time required for 60% of a sample of radon undergo decay. Given `T_(1//2)` of radon = 3.8 days.

The position of an object moving along x axis is given by x =a+ bt^2 here a= 8.5 m, b = 2.5 ms^(-2) and t is time in second. Calculate the velocity at t = 0 and t = 2 s and also calculate average velocity between t = 2 s and t = 4 s.

Calculate the average life of 79^(Au^(198)) leaving t^(1//2) = 150 days.