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Vedmedyk [2.9K]

3 years ago

6

The food calorie, equal to 4186 J, is a measure of how much energy is released when food is metabolized by the body. A certain b

rand of fruit-and-cereal bar contains 150 food calories per bar. Part A If a 68.0 kg hiker eats one of these bars, how high a mountain must he climb to "work off" the calories, assuming that all the food energy goes only into increasing gravitational potential energy?

1 answer:

rewona [7]3 years ago

5 0

Answer:

The hiker has to climb 941.26 to ''work off'' the calories.

Explanation:

Let's first find out how much energy the hiker gets from 150 food calories.

This is:

Energy = 150 * 4186

Energy = 627.9 kJ

To burn all of this off, we set it equal to the gravitational potential energy, and then solve for the height.

This is:

Gravitational Potential Energy (G.P.E) = 629700

G.P.E = mass * gravity * height

Thus,

mass * gravity * height = 629700

68 * 9.81 * height = 629700

height = 941.26 meters

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You push on a cart (18.0kg) at a 30 degree below horizontal angle. The coefficient of kinetic friction between the chair and the

podryga [215]

Given that force is applied at an angle of 30 degree below the horizontal

So let say force applied if F

now its two components are given as

$F_x = Fcos30$

$F_y = Fsin30$

Now the normal force on the block is given as

$N = Fsin30 + mg$

$N = 0.5F + (18\times 9.8)$

$N = 0.5F + 176.4$

now the friction force on the cart is given as

$F_f = \mu N$

$F_f = 0.625(0.5F + 176.4)$

$F_f = 110.25 + 0.3125F$

now if cart moves with constant speed then net force on cart must be zero

so now we have

$F_f + F_x = 0$

$Fcos30 - (110.25 + 0.3125F) = 0$

$0.866F - 0.3125F = 110.25$

$F = 199.2 N$

so the force must be 199.2 N

8 0

3 years ago

VLD [36.1K]

Answer:

Wilhelm Conrad Roentgen (1845-1923)

Antoine Henri Becquerel (1852-1908)

Pierre (1859-1906) and Marie (1867-1934) Curie

Explanation:

Wilhelm Conrad Roentgen (1845-1923)

Contribution: Discovery of x-rays in 1901.

Antoine Henri Becquerel (1852-1908)

Contribution: He discovered that radioactivity is the separation of x-rays and document and the difference between two.

Pierre (1859-1906) and Marie (1867-1934) Curie

Contribution: She discovered Polonium and Radium in1911

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3 years ago

When two substances are mixed together, a color change is observed. Does this mean that a chemical reaction has definitely occur

Elanso [62]

Nope, color change can also occur during a physical change.

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3 years ago

In what do electromagnetic waves cause disturbances when they transfer

IrinaVladis [17]

Both electric and magnetic fields

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3 years ago

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The photon energies used in different types of medical x-ray imaging vary widely, depending upon the application. Single dental

pav-90 [236]

A) $5.0\cdot 10^{-11} m$

The energy of an x-ray photon used for single dental x-rays is

$E=25 keV = 25,000 eV \cdot (1.6\cdot 10^{-19} J/eV)=4\cdot 10^{-15} J$

The energy of a photon is related to its wavelength by the equation

$E=\frac{hc}{\lambda}$

where

$h=6.63\cdot 10^{-34}Js$ is the Planck constant

$c=3\cdot 10^8 m/s$ is the speed of light

$\lambda$ is the wavelength

Re-arranging the equation for the wavelength, we find

$\lambda=\frac{hc}{E}=\frac{(6.63\cdot 10^{-34} Js)(3\cdot 10^8 m/s)}{4\cdot 10^{-15}J}=5.0\cdot 10^{-11} m$

B) $2.0\cdot 10^{-11} m$

The energy of an x-ray photon used in microtomography is 2.5 times greater than the energy of the photon used in part A), so its energy is

$E=2.5 \cdot (4\cdot 10^{-15}J)=1\cdot 10^{-14} J$

And so, by using the same formula we used in part A), we can calculate the corresponding wavelength:

$\lambda=\frac{hc}{E}=\frac{(6.63\cdot 10^{-34} Js)(3\cdot 10^8 m/s)}{1\cdot 10^{-14}J}=2.0\cdot 10^{-11} m$

4 0

2 years ago