Physics, 28.06.2019 00:30 andrew763

Homework for tommorow( quickly)a) a swimming pool contains 30000 kg of water at 8 celsius degreesspecific heat capacity of water = 4181 j/kg celsius degrees1) how much thermal energy is needed to raise the temperature of the water to 15 celsius degrees? 2) on a sunny day, the concrete at the side of the pool feels much hotter than the water, even though both have received the same thermal energy from the sun. explain fully why the concrete is hotterb) describe 2 ways you could increase the efficiency of a household central heating system

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Answer from: sctenk6052

(1) Use the formula

(energy E) = (specific heat capacity c) x (mass m) x (change in temperature T)

$E_{thermal} = c\cdot m\cdot \Delta T= 4181 \frac{J}{kg\cdot^\circ C}\cdot 30000kg\cdot 7 ^\circ C=878010000 J\approx 0.88\cdot10^9J = 0.88GJ$

To raise the temperature of the water by 7 degrees Celsius, about 0.88GJ (Gigajoules) of thermal energy is needed.

(2) There are multiple reasons for the observation: Water and concrete have different specific heat capacity, namely that of water is about 4 times higher than one of concrete, so given the same amount of thermal energy, the temperature rises only about a quarter with water as compared to concrete. Another factor in the difference is that while it suffices to heat a relatively thin surface layer of the concrete (i.e., small volume) for it to feel hot to touch, heating the water involves heating a larger volume at a time due to its continuous mixing with lower layers (since it is a liquid with low viscosity).

(3) (a) Install thermal insulation around ducts to minimize thermal energy loss. (b) consider installing multiple heating zones to increase focus of heating to areas that need heating at a given time. (There are many other possible ways, these are just suggestions)

Answer from: Quest

sleep paralysis is a parasomnia, events associated with sleep.

sleep paralysis happens when you are in the middle of waking up or falling asleep. it is the feeling of being conscious but unable to move. it definitely involves hallucinations.

i had a friend that had sleep paralysis and he told me a story one time where he was laying in bed and he couldn't move his body no matter how hard he tried and there was someone standing in the corner of his room coming towards him. he couldn't move and you can't "wake up" because you are already conscious. sometimes sleep paralysis can be triggered by frequent waking up during the night based off of multiple trips to the bathroom, or if you had ever been abused, sleep paralysis can start happening from things like that.

Answer from: Quest

1 a

2 b

3 b

4 d

5 d

6 d

explanation:

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Homework for tommorow( quickly)a) a swimming pool contains 30000 kg of water at 8 celsius degreessp...

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