The whale, swimming under water at a speed of 18 km / h, developed a power of 150 kW.

The whale, swimming under water at a speed of 18 km / h, developed a power of 150 kW. Find the strength of water resistance.

V = 18 km / h = 5 m / s.

N = 150 kW = 150,000 W.

Fsopr -?

We will assume that a whale swims uniformly in a straight line under water, then, according to Newton’s 1 law, the action of forces on it is compensated.

In the horizontal direction, the whale’s thrust force F is compensated by the water resistance force Fcop: F = Fcop.

The power of a whale N is called the ratio of mechanical work A to the time of its execution t: N = A / t.

A = F * S, where F is the whale’s pulling force, S is the whale’s movement.

The whale’s speed V is the ratio of its movement S to time t: V = S / t.

N = F * S / t = F * V.

F = N / V.

Fcopr = N / V.

Fcopr = 15000 W / 5 m / s = 3000 N.

Answer: under water, the whale is affected by a resistance force Fcoop = 3000 N.