Question

You throw a small rock straight up from the edge of a highway bridge that crosses a river. The rock passes you on its way down, 7.00 s after it was thrown. What is the speed of the rock just before it reaches the water 23.0 m below the point where the rock left your hand? Ignore air resistance.

Answer 1

A dummy is fired vertically upward from a canon with a speed of 40 m/s. How long is the dummy in the air? What is the dummies maximum height?

v=u-at

0=40-10xt

t=4 secs

height = ut-1/2at^2

height= 40x4-1/2x10x4^2

height = 160-5x16

height=160-80=80m