Question

A man stands at the top of a 27-m high building and throws a penny straight downward. If the penny has an initial velocity of -3.9 m/s, what is the velocity of the penny in m/s when it hits the ground?

Answer 1

A man stands at the top of a 27-m high building and throws a penny straight downward. If the penny has an initial velocity of -3.9 m/s, what is the velocity of the penny in m/s when it hits the ground?

Answer 2

Assumption: no air resistance.
Since the downwards direction is stated as negative, acceleration due to gravity is -10m/s2. using a=(v-u)/t, a being -10, u being initial velocity, v as velocity when hits the ground, t as time, u get t=(3.9-v)/10. find another value of such with 27=0.5 x (v+u) x t. get this equation and sub it to the previous one which is t=... to get the ans.