Acement block accidentally falls from rest from the ledge of a 80.6-m-high building. when the block is 10.8 m above the ground, a man, 2.10 m tall, looks up and notices that the block is directly above him. how much time, at most does the man have to get out of the way?

In which situation has the independent variable for the experiment been changed? check all that apply. changed from counting the number of duckweed at day 0 and day 14 to counting them every day changed from testing duckweed growth in beakers to testing duckweed growth in large outdoor tanks changed from testing the effect of ph on duckweed growth to testing the effect of light levels on duckweed growth changed from testing the effect of acid ph on duckweed growth to testing the effect of basic ph on duckweed growth

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

Is the vertical component of velocity ever zero?