The displacement x of a particle of rest mass m0, resulting from a constant force m0g along the x-axis, is
x= c2/g{[1+(gt/c)2]^0.5-1}

including relativistic effects. find the displacement x as a power series in time t. compare with the classical result, x = 1/2 gt2.

A12-g wad of sticky clay is hurled horizontally at a 100-g wooden block initially at rest on a horizontal surface. the clay sticks to the block. after impact, the block slides 7.5 m before coming to rest. if the coefficient of friction between the block and the surface is 0.65, what was the speed of the clay immediately before the impact?