Question

A girl drops a rock straight down from a bridge. Assume negligible air resistance. How fast is it going 4.0 s later?
(2 marks)

Answer 1

If a stone is thrown straight down at an initial zero speed, the speed of fall can be described by the equation

v=gt,

where g=9.8 m/s^2 is acceleration of gravity; t is time. Therefore, after 4 seconds of falling, the speed is equal to

v=9.8×4=39.2 m/s