The girl walks at a speed of 1 m / s along a horizontal road and pulls the sled behind her with a rope

The girl walks at a speed of 1 m / s along a horizontal road and pulls the sled behind her with a rope making an angle of 30 degrees with the horizon. The rope pulling force is 34 H. What power does the girl spend to move the sled?

V = 1 m / s.

∠α = 30 °.

F = 34 N.

N -?

Power N is called a scalar physical quantity that shows the speed of performing mechanical work. Power N is determined by the formula: N = A / t.

We express the mechanical work A by the formula: A = F * S * cosα, where F is the force that acts on the sleigh, S is the movement of the sleigh, ∠α is the angle between the force F and the movement S.

N = F * S * cosα / t.

With uniform rectilinear movement, the ratio of the distance traveled S to time t is called the speed of movement V: S / t = V.

The formula for the power will take the form: N = F * V * cosα.

N = 34 N * 1 m / s * cos30 ° = 29.5 W.

Answer: the girl spends power N = 29.5 watts to move the sled.