A horizontal force of 80 N is required to push a bookcase across a floor at a constant velocity. How much friction acts on the bookcase when it is at rest on a horizontal surface without being pushed?

Aplane travels 1000 miles in 5 hours .what is the planes average speed?

Determine the maximum r-value of the polar equation r =3+3 cos 0

In a simplified model of the human eye, the aqueous and vitreous humors and the lens all have a refractive index of 1.40, and all the refraction occurs at the cornea, whose vertex is 2.60 cm from the retina. what should be the radius of curvature of the cornea such that the image of an object 40.0 cm from the cornea’s vertex is focused on the retina?