Question

write the scientific name of cockroach and Prawns a boy of mass 50 kg runs up a staircase of 45 steps in 9 seconds if the height of each step is cm find his power.take g=10m s-2 ii a battery lights a bulb .describe the energy changes involved in this process

Answer 1

Scientific names of :-

Cockroach : - $Periplaneta . americana$

Prawns : - $Dendrobranchiata$

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Mass of the boy =50 kg

Time taken = 9 sec

Height of 1 step = 15 cm = 0.15 metres

Height of 45 steps = 0.15 x 45 = 6.75 metres

We know that ,
$Power = \frac{Energy}{Time}$


Energy = Potential energy = mgh

= 50 x 10 x 6.75
= 3375 Joules

Power = $\frac{3375}{9}$

= 375 Watts

Hence , power of the boy is 375 Watts
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Energy transformations :-

The chemical energy of the battery is transformed into electrical energy.This electrical energy , which will be received by the bulb , gets converted to light and heat energy of the bulb.

Chemical energy --> Electrical energy -->Light energy + Heat energy