What are base isolators and give an example of an earthquake proof building

Energy is the ability to do work which measures what

Avery hard rubber ball (m = 0.5 kg) is falling vertically at 4 m/s just before it bounces on the floor. the ball rebounds back at essentially the same speed. if the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?

Determine the maximum r-value of the polar equation r =3+3 cos 0