Compare the power at which each of the following is moving upwards against the force of gravity? $(given\ g=10\ ms^{-2})$
1. A butterfly of mass $1.0\ g$ that flies upward at a rate of $0.5\ ms^{-1}$.
2. A $250\ g$ squirrel climbing up on a tree at a rate of $0.5\ ms^{-1}$.

1. As given, mass of butterfly $m_b=1\ g=10^{-3}\ kg$

Upward speed of butterfly $v_b=0.5\ ms^{-1}$

Force applied by the butterfly to fly upward $F_b=m_b. g$

$=10^{-3}\ kg\times 10ms^{-2}$

$=10^{-2}\ N$

So, power of butterfly $P_b=F_b. v_b$

$=10^{-2}\times 0.5$

$=0.005\ W$

Therefore, the power of the butterfly is $0.005\ W$.

2. Mass of the squirrel $m_s=250\ gm=0.25\ kg$

Velocity of the squirrel $v_s=0.5\ ms^{-1}$

 Force of gravity to climb $F_s=m_s. g$

$=0.25\ kg\times 10\ ms^{-2}$

$=2.5\ N$

So, power of squirrel $P_s=F_s.v_s$

$=2.5\ N\times 0.5\ ms^{-1}$

$=1.25\ W$

Therefore, the squirrel has greater power than the butterfly.

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Updated on: 10-Oct-2022

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