Question

A 10.0-kg microwave oven is pushed 7.00 m up the sloping surface of a loading ramp inclined at an angle of 36.9 ? above the horizontal, by a constant force F with a magnitude 109 N and acting parallel to the ramp. The coefficient of kinetic friction between the oven and the ramp is 0.259.

A.What is the work done on the oven by the force F? ?

B.What is the work done on the oven by the friction force?

C.Compute the increase in potential energy for the oven.

D.Use your answers to parts A, B, and C to calculate the increase in the oven's kinetic energy.

E.Use ?F? =ma?  to calculate the oven's acceleration.

F.Assuming that the oven is initially at rest, use the acceleration to calculate the oven's speed after the oven has traveled distance 7.00 m .

G.From this, compute the increase in the oven's kinetic energy. Take the free fall acceleration to be 9.80m/s^2 . Express your answer using two significant figures.

Answer 1

a) work done on the oven by the force F= 109 N ( 7m) =763 J

b) work done on the oven by the friction force = 0.259 ( 10) (9.8) cos 36.9 ( 7) = 142.1 J

c)gain in PE =mgh = 10 (9.8) ( 7 sin 36.9) =411.9 J

d) work done = change in enegry

763 J - 142.1 J = 411.9 + incresae in KE

621= 411.9 + incresae in KE

Increase in KE = 209.1 J

e)F= ma

109- mgsintheta - mu mg cos theta= ma

109 - 10(9.8)sin36.9 - 0.259 ( 10) (9.8) cos 36.9=10(a)

109 - 98 ( sin 36.9 + 0.259 cos 36.9)=10a

10.9 - 7.91 = a

f)a= 3 m/s^2

v = sqroot ( 2as)= sqroot ( 2x 3 x7)=6.48 m/s

g) 1/2mv^2= 1/2 (10) 6.48^2= 210 J