Physics, 11.02.2020 01:09 francisebell2p698f2

A rock can be launched toward a wall from ground level with initial velocity of v = (3i+4j)m/s. The distance between the launch site and the wall is 15 meters. What are the least speed an the greatest speed with which the rock can hit the wall?

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Answer from: leannamat2106

The rock will never reach the wall

Explanation:

Projectile Motion

When an object is launched with an initial velocity that has both horizontal and vertical components, it describes a parabola in the air and eventually returns to the ground after reaching its maximum height.

We have the initial velocity as

$v_o=(3\hat i+4\hat j)\ m/s$

And we also know the launching site is 15 meters away from the wall. That's all we need to know when the rock reaches the wall (if it does). The horizontal distance is

$x=v_{ox}.t$

Where vox is the horizontal component of the initial velocity. Solving for t

$\displaystyle t=\frac{x}{v_{ox}}$

$\displaystyle t=\frac{15}{3}=5\ sec$

We'll show this is an absurd time given the conditions of the problem. The height of the rock is computed by

$\displaystyle y=v_{oy}.t-\frac{gt^2}{2}$

If we use the value of t previously found

$\displasystyle y=4\times 5-\frac{9.8\times 5^2}{2}$

$y=-102.5\ m$

This means the rock will never reach the wall since it lands on the ground way before that. The problem has no solution

Answer from: Quest

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Answer from: Quest

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.

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A rock can be launched toward a wall from ground level with initial velocity of v = (3i+4j)m/s. The...