Physics, 03.08.2019 15:50 smithsa10630

Suppose you look out the window of a skyscraper and see someone throw a tomato downward from above your window. your window is at a height of 450 feet above the ground. the tomato passes your window after 2 seconds and hits the ground 5 seconds after it was thrown. neglect air resistance, and give units in your answers. (a) find the velocity (with the positive direction pointing up) at which the tomato was thrown.

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Answer from: madisynk78

The velocity at which the tomato was thrown is -38 m/s and the direction is downwards.

The given parameters;

height of the window, h = 450 ftfirst time to pass the window, t = 2 secondstime to hit the ground = 5 seconds

The height traveled by the tomato at the given time is calculated as follows;

$h = h_0 + v_0t - \frac{1}{2} gt^2$

where;

g is acceleration due to gravity = 32 ft/s²

when the time is 2 seconds;

$450 = h_0 + 2v_0 \ - \ (0.5 \times 32 \times 2^2)\\\\450 = h_0 + 2v_0 - 64\\\\450 + 64 = h_0 + 2v_0\\\\514 = h_0 + 2v_0\\\\h_0 = 514 - 2v_0 \ \ ---(1)$

when the time is 5 seconds;

$0 = h_0 + 5v_0 - (0.5 \times 32 \times 5^2)\\\\0 = h_0 + 5v_0 -400\\\\400 = h_0 + 5v_0$

from equation 1, the initial velocity of the ball is calculated as follows;

$400 = h_0 + 5v_0\\\\ 400 = (514 - 2v_0) + 5v_0\\\\400 = 514 - 2v_0 + 5v_0\\\\400-514 = 3v_0\\\\-114 = 3v_0\\\\\v_0 = \frac{-114}{3} \\\\v_0 = -38 \ m/s$

Thus, the velocity at which the tomato was thrown is -38 m/s and the direction is downwards.

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Answer from: camimilligan114

Formula for height
r(t) = a/2 t² + v₀ t + r₀
where
a = acceleration = -32 ft/sec² (gravity)
v₀ = initial velocity
r₀ = initial height
r(t) = -16t² + v₀ t + r₀
Tomato passes window (height = 450 ft) after 2 seconds:
r(2) = 450
-16(4) + v₀ (2) + r₀ = 450
r₀ = 450 + 64 - 2v₀
r₀ = 514 - 2v₀
Tomato hits the ground (height = 0 ft) after 5 seconds:
r(5) = 0
-16(25) + v₀ (5) + r₀ = 0
r₀ = 16(25) - 5v₀
r₀ = 400 - 5v₀

r₀ = 514 - 2v₀ and r₀ = 400 - 5v₀
514 - 2v₀ = 400 - 5v₀
5v₀ - 2v₀ = 400 - 514
3v₀ = −114
v₀ = −38
Initial velocity = −38 ft/sec (so tomato was thrown down)
(initial height = 590 ft)

Answer from: Quest

current and voltage can both be different in different parts of a circuit so it matters where you place the ammeter and voltmete

Answer from: Quest

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

so, refractive index of medium = 300000/200000 = 1.5

1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

∞ refractive index is usually for opaque mediums. so third medium is opaque medium.

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