Question

Compare the power at which each of the following is moving upwards against the force of gravity? (given g = 10 m s^–2)

a butterfly of mass 1.0 g that flies upward at a rate of 0.5 ms^–1.

Answer 1

Mass of butterfly, mb = 1 g = 10⁻³ kg

Speed, vb = 0.5 m s⁻¹

Force of gravity on butterfly, Fh = mbg

= 10⁻³ × 10

= 10⁻² N

Power, P_b = F_b. v_b

= 10⁻² N × 0.5 m s⁻¹ 

= 0.005 W