Question

A 2.5 kg hammer falls from a scaffold on a building 60.0 m above the ground.

(a) Find its potential energy before it falls.

(b) If all the potential energy was converted to kinetic energy, find the speed of the hammer as it hits the ground.

(c) Find its kinetic energy the instant before it hits the ground.

Answer 1

Given :

m = mass of hammer = 2.5 kg

h = height = 60 m

a) Potential energy Before it falls is = U = mgh = 2.5*9.81*60 = 1471.5 J [answer]

b) Let the speed when it hits the ground is v.

As the motion is acclerated under gravity.

Applying kinematic equation :

   [answer]

c) Kinetic energy is given by [answer]

alternatively : Applying consrvation of mechanical transfre

gain in kinetic energy = loss in potential energy

=> K = 1471.5 J. [answer]