Alisha starts pulling (from rest) a box full of books on a horizontal floor. She has tied the rope to the box, the rope makes an angle of 40.0° relative to the floor. She pulls with a force F of magnitude 120N. The total mass of the box is 50.0kg. She pulls the box in a straight line over a distance of 6.00m. There is 70.0N friction force between the floor and the box. Calculate the final speed of the box

1 answer

F = 120N[40o].
Fk = 70 N.
d = 6.0 m.

F*Cos40 - Fk = M*a.
120*Cos40 - 70 = 50a,
a = 0.439 m/s^2.

V^2 = Vo^2 + 2a*d = 0 + 2*0.439*6 = 5.27,
V = 2.30 m/s.