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MA_775_DIABLO [31]

3 years ago

13

It turns out that most of the electricity we use in Ohio comes from burning coal. Coal yields about 30 Gigajoules (GJ = 109 J) o

f electricity per metric ton (1000 kg). Assuming that the coal plant is 30% efficient (i.e. the plant captures 30% of the energy converted by burning coal), how much total coal has to be burned to keep that 100 W light bulb lighted for the week?

1 answer:

rodikova [14]3 years ago

5 0

Answer:

0.6048 kg of coal

Explanation:

Mass energy input = mass energy output/efficiency

Mass energy output = 30 GJ/ton= 3×10^10 J/1000 kg = 3×10^7 J/kg

Efficiency = 30% = 0.3

Mass energy input = 3×10^7/0.3 = 1×10^8 J

Mass of coal to be burned = power×time/mass energy input

Power = 100 W

Time = 1 week = 604,800 s

Mass of coal to be burned = 100×604,800/1×10^8 = 0.6048 kg

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The maximum distance from the Earth to the Sun (at aphelion) is 1.521 1011 m, and the distance of closest approach (at perihelio

LUCKY_DIMON [66]

Answer:

29274.93096 m/s

$2.73966\times 10^{33}\ J$

$-5.39323\times 10^{33}\ J$

$2.56249\times 10^{33}\ J$

$-5.21594\times 10^{33}$

Explanation:

$r_p$ = Distance at perihelion = $1.471\times 10^{11}\ m$

$r_a$ = Distance at aphelion = $1.521\times 10^{11}\ m$

$v_p$ = Velocity at perihelion = $3.027\times 10^{4}\ m/s$

$v_a$ = Velocity at aphelion

m = Mass of the Earth = 5.98 × 10²⁴ kg

M = Mass of Sun = $1.9889\times 10^{30}\ kg$

Here, the angular momentum is conserved

$L_p=L_a\\\Rightarrow r_pv_p=r_av_a\\\Rightarrow v_a=\frac{r_pv_p}{r_a}\\\Rightarrow v_a=\frac{1.471\times 10^{11}\times 3.027\times 10^{4}}{1.521\times 10^{11}}\\\Rightarrow v_a=29274.93096\ m/s$

Earth's orbital speed at aphelion is 29274.93096 m/s

Kinetic energy is given by

$K=\frac{1}{2}mv_p^2\\\Rightarrow K=\frac{1}{2}\times 5.98\times 10^{24}(3.027\times 10^{4})^2\\\Rightarrow K=2.73966\times 10^{33}\ J$

Kinetic energy at perihelion is $2.73966\times 10^{33}\ J$

Potential energy is given by

$P=-\frac{GMm}{r_p}\\\Rightarrow P=-\frac{6.67\times 10^{-11}\times 1.989\times 10^{30}\times 5.98\times 10^{24}}{1.471\times 10^{11}}\\\Rightarrow P=-5.39323\times 10^{33}$

Potential energy at perihelion is $-5.39323\times 10^{33}\ J$

$K=\frac{1}{2}mv_a^2\\\Rightarrow K=\frac{1}{2}\times 5.98\times 10^{24}(29274.93096)^2\\\Rightarrow K=2.56249\times 10^{33}\ J$

Kinetic energy at aphelion is $2.56249\times 10^{33}\ J$

Potential energy is given by

$P=-\frac{GMm}{r_a}\\\Rightarrow P=-\frac{6.67\times 10^{-11}\times 1.989\times 10^{30}\times 5.98\times 10^{24}}{1.521\times 10^{11}}\\\Rightarrow P=-5.21594\times 10^{33}$

Potential energy at aphelion is $-5.21594\times 10^{33}\ J$

6 0

3 years ago

Tres personas, A, B, C, jalan una caja con ayuda de cuerdas cuya masa es despreciable. Si la persona A aplica −3 en dirección ho

Yuri [45]

Answer:

El valor de la fuerza que debe ejercer la persona C debe ser de -2 para que la caja esté en equilibrio físico.

Explanation:

Si la caja debe hallarse en equilibrio físico, entonces se debe satisfacer la siguiente ecuación:

$F_{A} + F_{B} + F_{C} = 0$ (1)

Si sabemos que $F_{A} = -3$ y $F_{B} = 5$ , entonces el valor de la fuerza que debe ejercer la persona C debe ser:

$F_{C} = -F_{A}-F_{B}$

$F_{C} = -(-3)-5$

$F_{C} = -2$

El valor de la fuerza que debe ejercer la persona C debe ser de -2 para que la caja esté en equilibrio físico.

3 0

3 years ago

What happens when solar energy heats a body of water?

Nataliya [291]

Explanation: Evaporation happens when a liquid substance becomes a gas. When water is heated, it evaporates. The molecules move and vibrate so quickly that they escape into the atmosphere as molecules of water vapor (Dunn,1993).

6 0

3 years ago

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Which of the following is true of education in 1950

Maksim231197 [3]

Information I learned from history class Education in the 1950's expanded from previous decades. They no longer focused purely on reading, writing and arithmetic. History and science became a main part of the cirriculum. Also, enrollment skyrocketed as the baby-boomers began enrolling in elementary school. One interesting thing that categorized this generation was the presence of fallout tests. Schools would require the students to go through a fake atomic bomb attack in which they would hide under their desks (which was completely pointless in protecting them from radiation, it was more of an emotional security for the parents and teachers, but scared the hell out of the students). Socially, children were taught to conform and to be normal. Standing out or questioning authority was bad. Sex was taught, though minimally. They explained the penis and vagina. Sexually transmitted diseases were focused on greatly so as to "scare" the students out of premarital sex.

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3 years ago

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timofeeve [1]

Answer:

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7 0

3 years ago