A hummingbird hovers by exerting a downward force on the air equal, on average, to its weight. By Newton's third law, the air exerts an upward force of the same magnitude on the bird's wings. Find the average mechanical power (in W) delivered by a 2.80 g hummingbird while hovering if its wings beat 55.0 times per second through a stroke 3.34 cm long. HINT

It takes 1700 J of work to stretch a spring from its natural length of 1 m to a length of 5 m. Find the force constant of the spring. The spring's force constant is N/m. (Type an integer or a simplified fraction.)

A hummingbird hovers by exerting a downward force on the air equal, on average, to its weight. By Newton's third law, the air exerts an upward force of the same magnitude on the bird's wings. Find the average mechanical power (in W) delivered by a 3.60 g hummingbird while hovering if its wings beat 75.0 times per second through a stroke 3.98 cm long. HINT To find the average power per stroke, calculate the work done each stroke and divide by the time per stroke. Click the hint button again to remove this hint.

A tank has the shape of an inverted right circular cone with height 9m and radius 18m. It is filled with 5m of hot chocolate. Assume that the density of the hot chocolate is 1450kg/m^3 and g=9.8m/s^2.Find the work required to empty the tank by pumping the hot chocolate over the top of the tank.Work =  Joules.