A 65 kg speed skater is racing around a circular track. The track has a radius of 20 m. It takes the skater 10 seconds to complete one lap. The skater moves at a pace of 12.56 m/s. Calculate the skater's acceleration.

Alfred pushes on a heavy box, but cannot move it. the box has a lot of inertia motion friction gravity

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?

I’ve been stuck on this for a while