Physics, 10.03.2020 07:41 mia5530

A 1400 kg car drives up a 16 m high hill. The car’s speeds at the bottom and top are 21 m/s and 13 m/s, respectively. If the car's engine does 80 kJ of work then what is the work done by friction?

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Answer from: mmcdaniels46867

Explanation:

mass, m = 1400 kg

height, h = 16 m

initial velocity, u = 21 m/s

final velocity, v = 13 m/s

Work done by engine, We = 80 kJ

Let the work done by the friction force is Wf.

Use the work energy theorem

net work done = change in kinetic energy

work done by engine + work done by friction force + work done by the gravitational force = Change in kinetic energy

80000 + Wf - m x g x h = 0.5 m ( v² - u²)

80000 + Wf - 1400 x 9.8 x 16 = 0.5 x 1400 x ( 169 - 441 )

- 139520 + Wf = - 190400

Wf = 50880 J

Answer from: Quest

Answer:

the word that best describes martin luther king jr.'s tone in the video is dignified

explanation:

martin luther king, jr. was a social activist and baptist minister who played a key role in the american civil rights movement from the mid-1950s until his assassination in 1968. the video shows his manner and attitude having or showing a composed or serious manner that is worthy of respect so dignified is the correct answer

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 1400 kg car drives up a 16 m high hill. The car’s speeds at the bottom and top are 21 m/s and 13 m...

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