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3 years ago

9

A car is raised a certain distance in a service-station lift, thus giving it potential energy relative to the floor. if it were

raised twice as high, how much more potential energy would it have?

1 answer:

Lina20 [59]3 years ago

8 0

Potential energy is directly proportional to height. Double the height, you double the potential energy.

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An engine draws energy from a hot reservoir with a temperature of 1250 K and exhausts energy into a cold reservoir with a temper

bixtya [17]

Answer:

a. $P=18.61\ W$

b. $\eta_c=0.6976=69.76\%$

c. $\eta=0.4718=47.18\%$

Explanation:

Given:

temperature of the hotter reservoir, $T_H=1250\ K$

temperature of the colder reservoir, $T_C=378\ K$

heat absorbed by the engine, $Q_H=1.42\times 10^{5}\ J$

heat rejected to the cold reservoir, $Q_L=7.5\times 10^4\ J$

time duration of the energy transfer, $t=1\ hr=3600\ s$

<u>Now the work done by the engine:</u>

Using energy conservation,

$W=Q_H-Q_L$

$W=14.2\times 10^4-7.5\times 10^4$

$W=6.7\times 10^4\ J$

a.

<u>Hence the power output:</u>

$P=\frac{W}{t}$

$P=\frac{6.7\times 10^4}{3600}$

$P=18.61\ W$

b.

$\eta_c=1-\frac{T_L}{T_H}$

$\eta_c=1-\frac{378}{1250}$

$\eta_c=0.6976=69.76\%$

c.

now actual efficiency:

$\eta=\frac{W}{Q_H}$

$\eta=\frac{6.7\times 10^4}{1.42\times 10^{5}}$

$\eta=0.4718=47.18\%$

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3 years ago

Which of the following is a benefit of physical activity?

zaharov [31]

Answer:

B

Explanation:

better concentration

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3 years ago

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What must you know in order to determine the gravitational force between two objects?

Ganezh [65]

You must know the masses of both objects and the gravitational constant used to calculate the gravitational force between the 2 objects.

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3 years ago

How do you find pressure related to temperature

Ivenika [448]

Temperature and pressure are directly proportional to each other. If this helps,please pick me the best. Also,please say thanks.

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3 years ago

The speed for a car that went a distance of 125 miles in 2 hours time is ______. Question 2 options: 250 meters/sec 62.5 miles/h

Goryan [66]

Answer:

62.5 miles per hour

Explanation:

Speed = Distance travelled / Time taken

Speed = 125/2 = 62.5

You derive the units of the speed...by using the speed formula....,

Speed = Distance/Time

Speed = miles/hour

Hence the units for the speed = miles/hour

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3 years ago