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lidiya [134]
3 years ago
6

A person holding a 30 kg box 1 m above the floor puts it down. How much work was done ? Remember , the force of an objects weigh

t = mass times gravity
A. 0.0j

B. 30j

C. 147 j

D. 294 j
Physics
2 answers:
IrinaK [193]3 years ago
4 0
Hey friend! The answer is D. 294 j
frosja888 [35]3 years ago
3 0
As long as the box was 1m off the floor. it's potential energy was m•g•h = 30•9.8 = 294 joules. When the person stopped restraining the box and allowed it to move, gravity did 294 joules of work on the box, and would have done more if the floor hadn't been in the way. The person did no work on the box.
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A camera is equipped with a lens with a focal length of 34 cm. When an object 2.4 m (240 cm) away is being photographed, what is
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Answer:

The magnification is -6.05.

Explanation:

Given that,

Focal length = 34 cm

Distance of the image =2.4 m = 240 cm

We need to calculate the distance of the object

\dfrac{1}{u}+\dfrac{1}{v}=\dfrac{1}{f}

Where, u = distance of the object

v = distance of the image

f = focal length

Put the value into the formula

\dfrac{1}{u}=\dfrac{1}{34}-\dfrac{1}{240}

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The magnification is

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When an electron in a certain excited energy level in a one-dimensional box of length 2.00 Å makes a transition to the ground st
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Unpolarized light of intensity I0 = 950 W/m2 is incident upon two polarizers. The first has its polarizing axis vertical, and th
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Answer:

Intensity of the light (first polarizer) (I₁) = 425 W/m²

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Explanation:

Given:

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Intensity of the light (second polarizer) (I₂) = (425)(0.1786)

Intensity of the light (second polarizer) (I₂) = 75.905 W/m²

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