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eduard
3 years ago
13

How much heat does a freezer need to remove from 1kg of water at 40°C to make ice at 0°C? (You will need to use the specific hea

t of water to drop the temperature first, before trying to make the phase change!) Show your work.
Physics
1 answer:
Montano1993 [528]3 years ago
3 0

Answer:

Explanation:

Q = m c Δt

heat withdrawn to lower temperature by 40° C

Q = 1 X 1000 X 40 = 40,000 calories.

Q = mL

heat withdrawn to freeze water at 0°C to ice

= 1 x 80000 = 80,000 calories

total heat to be withdrawn = 120,000 calories. = 120,000 x 4.2 = 504 ,000 Joules.

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Ou drag your feet on a carpeted floor on a dry day and the carpet acquires a net positive charge. a. Will you have an electron d
11Alexandr11 [23.1K]

Answer:

1) We will have excess of electrons

2) The number of electrons transferred equals 1.343\times 10^{10}

Explanation:

Part a)

Since we know that the charge transfer occurs by the transfer of electrons only as it is given that the carpet has acquired a positive charge it means that it has lost some of the electron's since electrons are negatively charged and if a neutral body looses negative charge it will become positively charged. The electron's that are lost by the carpet will be acquired by the feet of the human thus making us negatively charged.Hence we will gain electrons making us excess in electrons.

Part b)

From charge quantinization principle we have

Q=ne

where

Q = charge of body

n = no of electrons

e = fundamental charge

Applying values in the above equation we get

2.15\times 10^{-9}C=n\times 1.6\times 10^{-19}C\\\\\therefore n=\frac{2.15\times 10^{-9}C}{1.6\times 10^{-19}C}=1.343\times 10^{10}

4 0
3 years ago
A football was kicked so that it traveled 65 yards in 3.0 total seconds. What was the speed
Olin [163]

Answer:

vx = 65 yd/3 sec  = 21.7 yd/sec  since horizontal speed is constant

vy = g t = (32 / 3) yd/sec^2 * 1.5 sec = 16 yd/sec   where 32/3 is the acceleration due to gravity in yds / sec^2  and 1.5 is the time to travel each way in the vertical direction

V = (vx^2 + vy^2)^1/2 = (21.7^2 + 16^2)^1/2 = 27 yd/sec

tan theta = vy/vx = 16 / 21.7 = .737    theta = 36.4 deg

You can check using the range formula:

R = v^2 sin (2 theta) / g = 27^2 * .955 / (32 / 3) = 65.3 yds  

The difference from 65 yds may be rounding error.

4 0
4 years ago
For any string w = w1w2 · · · wn, the reverse of w, written w R, is the string w in reverse order, wn · · · w2w1. For any langua
Nata [24]

Answer:

Attached is a solution.

6 0
3 years ago
If you were to walk at a constant speed 20m/s for 30 seconds, how far would you walk?
lana [24]

Answer:

600m

Explanation:

30×20 at a constant speed is 600m.

6 0
4 years ago
Inside a car that was at 273 K, a bottle with a pressure at 100,000 pascals warms up to
Deffense [45]

Answer:

P2 = 128,205 pascal.

Explanation:

<u>Given the following data;</u>

Original Pressure, P1 = 100,000 pascals

Original Temperature, T1 = 273K

New Temperature, T2 = 350K

To find new pressure P2, we would use Gay Lussac' law.

<em>Gay Lussac's law states that when the volume of an ideal gas is kept constant, the pressure of the gas is directly proportional to the absolute temperature of the gas. </em>

Mathematically, Gay Lussac's law is given by;

PT = K

Where;

  • P represents pressure.
  • T represents temperature.
  • K is the constant of proportionality.

\frac{P1}{T1} = \frac{P2}{T2}

<em>Making P2 as the subject formula, we have;</em>

P_{2}= \frac{P1}{T1} * T_{2}

Substituting into the equation, we have;

P_{2}= \frac{100000}{273} * 350

P_{2}= 366.3004* 350

P2 = 128205.13 ≈ 128205 pascal.

<em>Therefore, the pressure inside the hot water bottle is 128,205 pascal. </em>

5 0
3 years ago
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