Question

A helicopter is hovering at an altitude of 1km when a panel from its underside breaks loose and plummets to the ground. The mass of the panel is 15kg and it its the ground with a speed of 45m/s. How much mechanical energy was dissipated by air resistance during the panel’s descent?

Answer 1

Answer:

The right answer is "131812.5".

Explanation:

The given values are:

Mass,

m = 15 kg

Velocity,

v = 45 m/s

As we know,

⇒  $PE_1=mgh$

On putting the values, we get

⇒          $=15\times 9.8\times 1000$

⇒          $=147000 \ J$

According to the question,

$KE_1=0 \ J$

$PE_f=0 \ J$

⇒  $KE_f=\frac{1}{2}\times 15\times 45^2$

⇒           $=\frac{1}{2}\times 15\times 2025$

⇒           $=15187.5 \ J$  

hence,

⇒  $PE_i=KE_f+W_{air}$

or,

⇒  $W_{air} = PE_i-KE_f$

⇒          $=147000-15137.5$

⇒          $=131812.5 \ J$