A rock is thrown straight up and passes by a window. The window is 1.7m tall, and the rock takes 0.22 seconds to pass from the bottom of the window to the top. How far above the top of the window will the rock rise?

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Answer:

The rock will rise 2.3 m above the top of the window

Explanation:

The equations for the position and velocity of the rock are the following:

y = y0 + v0 · t + 1/2 · g · t²

v = v0 + g · t

Where:

y = height of the rock at time t

v0 = initial velocity

y0 = initial height

g = acceleration due to gravity

t = time

v = velocity at time t

If we place the center of the frame of reference at the bottom of the window, then, y0 = 0 and at t = 0.22 s, y = 1.7 m. With this data, we can calculate v0:

1.7 m = 0.22 s · v0 - 1/2 · 9.8 m/s² · (0.22 s)²

Solving for v0:

v0 = 8.8 m/s

Now that we have the initial velocity, we can calculate the time at which the rock reaches its maximum height, knowing that at that point its velocity is 0.

Then:

v = v0 + g · t

0 = 8.8 m/s - 9.8 m/s² · t

-8.8 m/s / -9.8 m/s² = t

t = 0.90 s

Now, we can calculate the max height of the rock:

y = y0 + v0 · t + 1/2 · g · t²

y = 8.8 m/s · 0.90 s - 1/2 · 9.8 m/s² · (0.90 s)²

y = 4.0 m

Then the rock will rise (4.0 m - 1.7 m) 2.3 m above the top of the window

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