A person evenly pulls the sled with a force of 100 N directed at an angle of 60 ° to the horizon.

A person evenly pulls the sled with a force of 100 N directed at an angle of 60 ° to the horizon. If the sled moved 20 m in 10 s, then the useful power developed by a person is equal to

F = 100 N.

∠α = 60 °.

t = 10 s.

S = 20 m.

N -?

Power N is called a scalar physical quantity that shows how quickly mechanical work A. Power N is determined by the formula: N = A / t, where A is mechanical work, t is the time of work.

Mechanical work A is determined by the formula: A = F * S * cosα, where F is the force with which the sleigh is pulled, S is the movement of the sleigh, ∠α is the angle between the force F and the movement S.

The formula for determining the power N will take the form: N = F * S * cosα / t.

N = 100 N * 20 m * cos60 ° / 10 s = 400 W.

Answer: the useful power of a person is N = 400 W.