1.An automobile engine slows down from 3100 rpm to 1500 rpm in 2.0 s . A. Calculate its angular acceleration, assumed constant. Express your answer using two significant figures. B. Calculate the total number of revolutions the engine makes in this time. Express your answer as an integer. 2. A child rolls a ball on a level floor 3.1 m to another child. A. If the ball makes 13.0 revolutions, what is its diameter? Express your answer to two significant figures and include the appropriate units