Physics, 04.09.2019 00:20, shongmadi77

The engine of a locomotive exerts a constant force of 8.110^5 n to accelerate a train to 68 km/h. determine the time (in min) taken for the train of mass 1.910^7 kg to reach this speed from rest.

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answered: michelleperezmp58

443.1 s

Explanation:

Given

Engine of a locomotive exerts a force of $8.1\times 10^5 N$

Mass of train $=1.9\times 10^7$

Final speed (v) $=68 km/h \approx 18.88 m/s$

F=ma

so $acceleration(a) =\frac{F}{m}=\frac{8.1\times 10^5}{1.9\times 10^7}$

a=0.042631 m/s^2

and acceleration is

$a=\frac{v-u}{t}$

$0.042631=\frac{18.88-0}{t}$

$t=443.089 \approx 443.1 s$

answered: yfnal3x

Explanation:

It is given that,

Force acting on the engine, $F=8.1\times 10^5\ N$

Initial speed of the engine, u = 0 (at rest)

Final speed of the engine, v = 68 km/h = 18.88 m/s

Mass of the train, $m=1.9\times 10^7\ kg$

We need to find the time taken by the train. Firstly, we will find the acceleration of the engine from Newton's second law of motion as :

$a=\dfrac{F}{m}$

$a=\dfrac{8.1\times 10^5}{1.9\times 10^7}$

$a=0.042\ m/s^2$

Now using first equation of motion to find time taken as :

v=u+at

$t=\dfrac{v-u}{a}$

$t=\dfrac{18.88-0}{0.042}$

t = 449.52 seconds

t = 7.49 minutes

So, the time taken for the train to reach this speed is 7.49 minutes. Hence, this is the required solution.

answered: Guest

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.

answered: Guest

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