Achild throws a ball up in the air to a height of 3.5 m and catches it at the same point from which he threw it. the ball is in the air for a total of 1.7 s. what is the average velocity of the ball? explain your answer.

Henry, whose mass is 95 kg, stands on a bathroom scale in an elevator. the scale reads 830 n for the first 2.4 s after the elevator starts moving, then 930 n for the next 2.4 s. part a what is the elevator's speed 4.8 s after starting? express your answer with the appropriate units.