math help please !!!

posted by .

i really neeed help, i have no idea how to answer this question ! i tried everything i know!

A stone is thrown off a cliff. it reaches a maximum height of 30m after 2 seconds, then falls into the water below. it hits the water after 5 seconds

a) how high above the water is the cliff ( The maximum height is relative to water level )

b) what is the ' second zero' and what does it mean

  • math help please !!! -

    *reposted -- because i think you haven't read my previous post in this problem*

    first, we solve for the initial velocity from the formula of the maximum height:
    h,max = [(vo)^2]/(2g)
    where
    vo = initial velocity
    g = acceleration due to gravity = 9.8 m/s^2
    substituting,
    30 = [(vo)^2]/(2*9.8)
    vo = sqrt(588)
    vo = 24.25 m/s

    (a) note that the motion of the stone is uniformly accelerated motion, thus we can use the formula:
    h = ho + (vo)*t - (1/2)*g*t^2
    where
    h = final height
    ho = initial height
    t = time
    since the stone is thrown from the cliff, and making the water as reference, ho = the height of cliff, and h = 0. substituting,
    h = ho + (vo)*t - (1/2)*g*t^2
    0 = ho + (24.25)*(5) - (1/2)*9.8*(5^2)
    0 = ho - 1.25
    ho = 1.25 m

    (b) ..sorry but i don't know what second zero means~ ^^;

    anyway, hope this helps~ :)

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. math

    i really need help, i have no idea how to answer this question ! A stone is thrown off a cliff. it reaches a maximum height of 30m after 2 seconds, then falls into the water below. it hits the water after 5 seconds a) how high above …
  2. math

    really need help, i have no idea how to answer this question ! A stone is thrown off a cliff. it reaches a maximum height of 30m after 2 seconds, then falls into the water below. it hits the water after 5 seconds a) how high above …
  3. math

    really need help, i have no idea how to answer this question ! A stone is thrown off a cliff. it reaches a maximum height of 30m after 2 seconds, then falls into the water below. it hits the water after 5 seconds a) how high above …
  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

    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?
  6. Physics please help!!

    A stone is aimed at a cliff of height h with an initial speed of v = 64.0 m/s directed 55.0° above the horizontal, as shown in the Figure below by the arrow. The stone strikes at A, 7.31 s after launching. What is the height of the …
  7. civil engineering

    A stone (on the edge of the roof) thrown from the top of a building is given an initial velocity of 20.0 m/s straight upward. The building is 50.0 m high, as shown in Fig. 4. Using tA = 0 as the time the stone leaves the thrower’s …
  8. Math

    A stone was thrown from the top of a cliff. The height, H meters, of the stone above sea level t seconds after it was released is given by H=-5t+20t+60. a)How high is the cliff?
  9. physics

    a stone that is thrown near the surface of the earth. There is no air resistance. Position increases in the up direction. The initial velocity is 30 m/s at 30 degrees above the horizontal. what is the velocity when the stone reaches …
  10. SCIENCE

    A stone thrown from the top of a building is given an initial velocity of 40.0 m/s straight upward. The building is 70.0m high, and the stone just misses the edge of the roof on its way down, determine (A) The time at which the stone …

More Similar Questions