# Physics

posted by .

Two rocks are thrown off the edge of a cliff that is 15.0 m above the ground. The first rock is thrown upward, at a velocity of +12.0 m/s. The second is thrown downward, at a velocity of −12.0 m/s. Ignore air resistance.

Determine (a) how long it takes the first rock to hit the ground and (b) at what velocity it hits. Determine (c) how long it takes the second rock to hit the ground and (b) at what velocity it hits.

• Physics -

Both are solved the same way:

Hf=hi+vi*t-4.9t^2
put in hi (15), hf(zero), vi (either 12, or-12), and solve for t.
velocity? Vf=Vi-9.8t

## Similar Questions

1. ### Physics

A rock is thrown vertically upward with a speed of 11.0 from the roof of a building that is 70.0 above the ground. Assume free fall. In how many seconds after being thrown does the rock strike the ground?
2. ### physics.

a ball is thrown upward with an initial velocity of 38.9 m/s from the edge of a cliff of height H. The ball lands on the ground at the base of the cliff 12.8 s after it is thrown.
3. ### math

A ball is thrown from the edge of a cliff with an initial velocity of 60·m/s upward. Answer the following questions using + (upward) and - (downward) to indicate the direction of the velocity. Ignore air resistance and assume the …
4. ### physics

A rock is thrown vertically upward from the edge of a cliff. The rock reaches a maximum height of 20.6 m above the top of the cliff before falling to the base of the cliff, landing 6.44 s after it was thrown. How high is the cliff?
5. ### physics

two rock are thrown off the edge of a cliff one is thrown horizont at a speed of 25 m s the other dropped straight down. which stone will hit the ground first?
6. ### physics

A rock is thrown vertically upward from the edge of a cliff. The rock reaches a maximum height of 20.6 m above the top of the cliff before falling to the base of the cliff, landing 6.54 s after it was thrown. How high is the cliff?
7. ### physics

A rock is dropped from a treetop 19.6 m high, and then, 1.00 s later, a second rock is thrown down. With what initial velocity must the second rock be thrown if it is to reach the ground at the same time as the first?
8. ### Math

For this problem, a person standing on the edge of a cliff throws a rock directly upward. it is observed that 2 secs later the rock is at its maximum height (in feet) and that 5 secs after that (meaning 7 seconds after being thrown) …
9. ### Physics

A rock is thrown horizontally off of a cliff. It starts with a velocity of 4.2 m/s and the cliff is 68.2 m high. How long does the rock fall?