Why does light have greater velocity in rarer medium?

Aball is thrown vertically upwards from the top of a tower with a speed of 100m/s. it strikes the pound near the base of the tower after 25sec . the height of the tower is

Ivana walks 2km north then turns around and walks 3km south

Acopper sheet has a volume of 100 cm³. if the density of copper is 8.9 g/cm³, what is the mass of the sheet? a. 11 g b. 8.9 g c. 189 g d. 890 g