Question

A stone is dropped from the top of a tower. The stone hits the ground after 5 seconds. Find the height of the tower and the velocity with which the stone hits the ground.

Answer 1

Answer:

Straightforward high school physics homework question.

Assume: the tower is on Earth, and: the stone is released without imparting any initial velocity to it, i.e. it just falls, and: we can neglect air resistance.

s=ut+½at2

s is the distance, which is what we want to find, so the equation is already arranged in the form we need.

u is the initial velocity, which in this case is 0, so the first part of the expression (ut) is 0.

a is the acceleration, which in this case is Earth’s gravitational acceleration, ~9.81 metres per second per second.

t is the time, which we’re given: 5 seconds.

so s=½⋅9.81⋅52=122.625m

The final velocity is given by

v=u+at

We know u is 0, and we have a and t:

v=0+9.81⋅5=49.05ms−1