The speed of a projectile when it reaches its maximum height is 0. 42 times its speed when it is at half its maximum height. What is the initial projection angle of the projectile?.

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.

What happens to an isotope during radioactive decay?

Astone is dropped from the upper observation deck of a tower, 250 m above the ground. (assume g = 9.8 m/s2.) (a) find the distance (in meters) of the stone above ground level at time t. h(t) = (b) how long does it take the stone to reach the ground? (round your answer to two decimal places.) s (c) with what velocity does it strike the ground? (round your answer to one decimal place.) m/s (d) if the stone is thrown downward with a speed of 2 m/s, how long does it take to reach the ground? (round your answer to two decimal places.) s