Question

A worker drops a wrench from the top of a tower 77.1 m tall. What is the velocity when the wrench strikes the ground? The acceleration of grav- ity is 9.81 m/s 2 . Answer in units of m / s

Answer 1

y=1/2gt^2---->77.1=1/2*9.81t^2---->t=3.97---->v=gt----v=38.95m/s

Answer 2

Alternatively, the potential energy, m g h becomes kinetic energy
as it falls, so at the bottom, (1/2) m v^2 = m g h

v=sqrt(2 g h)

which had better agree with the preceding analysis result.