physics

A ball thrown straight up from the ground passes a window 5.6 m up. An observer looking out the window sees the ball pass the window again, going down, 3.4s later.

Find the velocity with which the ball was initially thrown.

  1. 👍 0
  2. 👎 0
  3. 👁 1,205
  1. Use:
    s(t) = s(0) + v(0) t - ½ g t²
    v(t) = v(0) - g t
    9 = 9.8[m/s²]

    Let the ball pass the window up at t=0[s] and down at t=3.4[s], so:
    v(3.4) = -v(0)
    v(3.4) = v(0) - 9.8×3.4[m/s]
    .: v(0) = 9.8×3.4/2 [m/s]
    v(0) = 16.66[m/s]

    This is the velocity at the window sill.
    Let the ball have been thrown at t = ŧ.
    s(ŧ) = -5.3[m/s]
    s(ŧ) = 16.66 ŧ - ½×9.8 ŧ²
    .: 4.9 ŧ² -16.66 ŧ - 5.3 = 0
    ŧ = (16.66±√(16.66²+4×4.9×5.3))/(2×4.9)
    ŧ = 1.7±1.993...[s]
    The negative root gives the time of throw, while the positive gives the time of return.
    .: ŧ ≈ -0.293...[s]

    Initial velocity at time of throw:
    v(ŧ) = v(0) - g ŧ
    .: v(ŧ) = 1.66 + 9.8 × 0.293...
    v(ŧ) = 6.57...[m/s]

    1. 👍 0
    2. 👎 0

Respond to this Question

First Name

Your Response

Similar Questions

  1. science

    a ball is thrown straight upward and returns to the thrower's hand after 3.00s in the air. A second ball is thrown at an angle of 30.0 deg with the horizontal. At what speed must the second ball be thrown so that it reached the

  2. college physics

    a tennis ball is thrown straight up with an initial velocity of 22.5 m/s. it is caught at the same distance above the ground. a). how long does it take to reach its maximum height? b). how high does the ball rise? c). at what

  3. Physics

    From the window of a building, a ball is tossed from a height y0 above the ground with an initial velocity of 8.00 m/s and angle of 20.0 degrees below the horizontal. It strikes the ground 3.00 s later. (a) If the base of the

  4. Physics

    Nicole throws a ball straight up. Chad watches the ball from a window 5.0m above the point where Nicole released it. The ball passes Chad on the way up, and it has a speed of 10m/s as it passes him on the way back down. How fast

  1. science

    two tall buildings are 200m apart .with what speed must a ball be thrown horizontally from the window 540 m above the ground in one building, so that it will enter a window 50m above the ground in the other?

  2. Physics

    A ball is thrown straight up in the air and passes a window 0.30s after being released. It takes 1.5s to go from the window to its maximum height and back down to the window. What was the initial velocity of the ball when it was

  3. Physics

    A water balloon is thrown straight down at 10.0 m/s from a second floor window, 5.00 m above ground level. 1) How fast is the balloon moving when it hits the ground? (Express your answer to three significant figures.)

  4. Calculus

    The height, s, of a ball thrown straight down with initial speed 32 ft/sec from a cliff 48 feet high is s(t) = -16t^2 - 32t + 48, where t is the time elapsed that the ball is in the air. What is the instantaneous velocity of the

  1. physics

    A ball is thrown straight upward from ground level with a velocity of 41 m/s How much time passes before the ball strikes the ground? Disregard air resistance.

  2. Physics

    A ball is thrown straight upward and returns to the thrower’s hand after 2.3 s in the air. A second ball is thrown at an angle of 60◦ with the horizontal. At what speed must the second ball be thrown so that it reaches the

  3. Physics

    A ball is thrown vertically upward from a window with an initial velocity of 10m/s. if it hits the ground below the window 5.0s later, what is the height of the window...can you tell me the steps on how to do this please...

  4. Physics

    A red ball is thrown down with an initial speed of 1.3 m/s from a height of 28.0 meters above the ground. Then, 0.6 seconds after the red ball is thrown, a blue ball is thrown upward with an initial speed of 24.7 m/s, from a

You can view more similar questions or ask a new question.