Question

A ball with a mass of 3kg is dropped from the top of a building this is 20m high. what is the velocity of the ball when it is 10m above the ground ?

Answer 1

Answer:

Velocity=14[m/s]

Explanation:

We can solve this problem by using the principle of energy conservation, where potential energy becomes kinetic energy.

In the attached image we can see the illustration of the ball falling from the height of 20 meters, at this time the potential energy will have the following value.

$Ep=m*g*h\\where:\\m=3[kg]\\h=20[m]$

$Ep=3*9.81*20\\Ep=588.6[J]$

When the ball passes through half of the distance (10m) its potential energy will have decreased by half as shown below.

$Ep=3*9.81*10\\Ep=294.3[m]$

If we know that potential energy is transformed into kinetic energy, we can find the value of speed.

$Ek=\frac{1}{2} *m*v^{2} \\therefore\\v=\sqrt{\frac{Ek*2}{m} } \\v=\sqrt{\frac{294.3*2}{3} } \\\\v=14[m/s]$