Answer to Question #287953 in Physics for wendy

Question

a) An object of mass 3 kg is dropped from the roof of a two-storey house and reaches the ground with a speed of 10 m/s. Neglecting friction, calculate:

 

i. the kinetic energy of the object when it reaches the ground.

 

ii. the potential energy of the object when it is on the roof.

 

iii. the height of the roof.

 

iv. the total mechanical energy of the object when it is 1 m above the ground.

Answer 1

In the equations below, KE_b is the kinetic energy at the bottom, PE_t is the potential energy on top of building.

$\text i.\space KE_b=\dfrac 12mv^2=150\text{ J}.\\\space\\ \text {ii}.\space PE_t=KE_b=150\text{ J}.\\\space\\ \text {iii}.\space h=PE_t/(mg)=5\text{ m}.\\\space\\ \text {iv}.\space ME=PE_t=KE_b=150\text{ J}.$