A 50 kg child is sitting on a scale on the floor of an elevator. The elevator starts at rest and accelerates down at a rate of a=−1 m/s2.Calculate the velocity of the elevator after 3 seconds.

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?