physics

posted by .

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?

I'm not sure how to find the initial velocity of the thrown rock, since it's not 0

What I have so far:

1st rock:
Yo=o
Yf=19.6 m
Vo=o
Vf=
T=
A= -9.80 m/s^2

I think I've found the final velocity and time of the 1st rock
(Vf^2=Vo^2-2g(Y-Yo)
or final velocity squared = initial velocity(0 m/s)^2 -2(9.80)(-19.6-0)
which is = to -19.6 m/s
Time = 2 seconds
(Vf=Vo-gt, Vf/Vo-g=T, -19.6 m/s /-9.80 m/s^2, 2 seconds

How do I find the initial velocity of a throw object when I know:
Yo=o
Yf=19.6 m
T= 2-1 = 1 second
A- /9.80 m/s^2

Thanks!

  • physics -

    Wess, there are 2 cases in this prob:
    Case 1
    U nid to find how long the first rock took to hit the ground: use the formular- s=ut+0.5gt^2 where s=19.6m, u=0, t=?
    I gor t=1.97s
    Case 2
    The second rock took 1.97s-1s to hit the grnd, use same formula & find u

  • physics -

    Thank you very much!

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Physics

    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 …
  2. physics

    A rock is thrown vertically upward from the ground with an initial speed 15m/s. a. how high does go?
  3. physics

    A rock is thrown vertically upward from the ground with an initial speed 15m/s. a. how high does go?
  4. physics

    A ball is dropped from a roof to the ground 4.00 m below. Exactly 0.400 s later, a rock is thrown downwards with some initial velocity. If the two objects hit the ground at exactly the same time, what was the initial speed of the rock?
  5. PHYSICS- Please Help :(

    A ball is thrown downwards at a velocity of 14m/s from a bridge. One second earlier a rock is dropped from the same bridge. a)When will the ball meet up with the rock. b)When will the ball meet up with the rock?
  6. Physics

    A rock is thrown vertically from the edge of a cliff that is 500 ft high. It takes 6.5 seconds for the rock to hit the ground at the base of the cliff. Assume air resistance is negligible. (a) What was the initial velocity (magnitude …
  7. Physics

    Example 1: (Rock A) is thrown against a larger stationary rock(Rock B). considering the following possibilities... 1. Rock A bounces off of Rock B 2. Rock A splits into two pieces off of Rock B 3. Rock A explodes into many pieces off …
  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

    Question 1) A rock is dropped from the top of a 100 meter tall cliff. A. ) How long will it take for the rock to reach the ground. B) What will be the velocity of the rock when it hits the ground?
  10. Science

    A rock is held steady over a cliff and dropped. 1.1 seconds later, another rock is thrown straight down at a speed of 12.1 m/s, and hits the first rock. How far have the rocks dropped before they collide?

More Similar Questions