please please help me. i just don't know how to do this problem...i've tried everything.?

Question

A box of books weighing 300 N is shoved across the floor of an apartment by a force of 410 N exerted downward at an angle of 35.6° below the horizontal. If the coefficient of kinetic friction between box and floor is 0.57, how long does it take to move the box 3.90 m, starting from rest?

Answer 1

hi

Fh = 410 N * cos(35.6*) = 333.37 N
Fv = 410 N * sin(35.6*) = 238,67

Fvv = 300 N + 238.67 N = 538.67 N
Fh friction = Fvv * 0.57 = 307.04 N
there is motion because Fh > Fh friction
:))

Fhh = Fh - Fhfriction = 26.33 N
a = (Fhh/Weight ) * g = 0.86 m/s^2

t = root ( 2*e / a) )
= root ( 2*3.90 / 0.86)
= root (9.060)
= 3.01 s

bye

Answer 2

it is a constant acceleration problem, but the applied force is resisted by friction.
first separate the applied force into horizontal and vertical components.
the weight of the box, plus the vertical part of the applied force equals the 'apparent' weight of the object. that weight times coef of friction is the drag of the box on the ground.
the horizontal part of the applied force minus the drag is the force that acctually accelerates the box.
once you have a value for the force accelerating the box, use f=ma to find it's acceleration. remember to divide the weight of the box by g to get its mass!
now that you have a, you should be able to find distance travelled by d=1/2at^2