Why do elements within a group have similar chemical properties

Can you think of a way a rock unit with an older fossil could be above a rock until with a younger fossil? describe the scenario.

Will give brainliest! jay rides his 2.0-kg skateboard. he is moving at speed 5.8 m/s when he pushes off the board and continues to move forward in the air at 5.4 m/s. the board now goes forward at 13 m/s.a. determine jay’s mass.b. determine the change in the internal energy of the system during this process.(express your answer to two significant figures and include the appropriate units.)

Need only answer if you think you know it