Friction in machines is commonly reduced by using what?

Which of the following is not am example of a polymer? protein nylon kevlar concreta

Standing side by side ,you and a friend step off a bridge at different times and fall for 1.6s to the water below.your friend goes first,and you follow after he has dropped a distance of 2.0m.when your friend hits the water,is the seperation between the two of you 2.0m or more than 2.0m? verify your answer with a calculation.

What is the final velocity of the initial velocity of 25 and -50?