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Vikentia [17]
3 years ago
12

Which statement explains how it is possible to carry books to school without changing the kinetic or potential energy of the boo

ks or doing any work?
a. by moving the book without acceleration and keeping the height of the book constant
b. by moving the book with acceleration and keeping the height of the book constant
c. by moving the book without acceleration and changing the height of the book
d. by moving the book with acceleration and changing the height of the book
Physics
1 answer:
Mamont248 [21]3 years ago
8 0

Answer:

a. by moving the book without acceleration and keeping the height of the book constant

Explanation:

FOR CONSTANT KINETIC ENERGY:

The kinetic energy of a body depends upon its speed according to its formula:

ΔK.E = (1/2)mΔv²

So, for Δv = 0 m/s

ΔK.E = 0 J

So, for keeping kinetic energy constant, the books must be moved at constant speed without acceleration.

FOR CONSTANT POTENTIAL ENERGY:

The potential energy of a body depends upon its height according to its formula:

ΔP.E = mgΔh

So, for Δh = 0 m/s

ΔP.E = 0 J

So, for keeping potential energy constant, the books must be moved at constant height.

So, the correct option is:

<u>a. by moving the book without acceleration and keeping the height of the book constant</u>

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Answer:

0.345m

Explanation:

Let x (m) be the length that the spring is compress. If we take the point where the spring is compressed as a reference point, then the distance from that point to point where the ball is held is x + 1.1 m.

And so the potential energy of the object at the held point is:

E_p = mgh

where m = 1.3 kg is the object mass, g = 10m/s2 is the gravitational acceleration and h = x + 1.1 m is the height of the object with respect to the reference point

E_p = 1.3 * 10 * (x + 1.1) = 13(x + 1.1) = 13x + 14.3 J

According to the conservation law of energy, this potential energy is converted to spring elastic energy once it's compressed

E_p = E_k = kx^2/2 = 13x + 14.3

where k = 315 is the spring constant and x is the compressed length

315x^2 = 26x + 28.6

315x^2 - 26x - 28.6 = 0

x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

x = \frac{26 \pm \sqrt{26^2 - 4*(-28.6)*315}}{2*315}

x = \frac{26 \pm 191.6}{630}

x = 0.345 m or x = -0.263 m

Since x can only be positive we will pick the 0.345m

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PART A ) For the electrostatic force we have that is equal to

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Here

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E = Electric Force

F=(1.6*10^{-19}C)(2750N/C)

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a = \frac{F}{m}

Here,

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Replacing,

a = \frac{4.4*10^{-16}N}{1.67*10^{-27}kg}

a = 2.635*10^{11}m/s^2

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a = \frac{v_f-v_i}{t}

There is not v_i then

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Answer:

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