The time, t, required to drive a fixed distance varies inversely as the speed, r. It takes 9 hr at a speed of 20 km/h to drive a fixed distance. How long will it take to drive the same distance at a speed of 23 km/h?

The speed of light in a material is 0.50 c. what is the critical angle of a light ray at the interface between the material and a vacuum?

Idon’t quite understand this problem

It is reasonable to assume that the bulk modulus of blood is about the same as that of water (2.2 gpa). as one goes deeper and deeper in the ocean, the pressure increases by 10000 pa for every meter below the surface. if a diver goes down 80.0 m in the ocean, by how much does each cubic centimeter of her blood change in volume? give the answer in cubic centimeters (actually one cubic centimeter equals one milliliter).