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3 years ago

What is the approximate percentage change in the Earth-Sun distance between June 21 and December 21?

1 answer:

5 0

For the purpose of the exercise, we can assume that the Earth is at perihelion (closest point to the Sun) on December 21st (in reality, it happens around January 4th) and that the Earth is at aphelion (farthest point from the Sun) on June 21st (in reality, this happens around July 4th). The distance Earth-Sun is the following:
- Perihelion: 147.1 milion km
- Aphelion: 152.1 milion km
- Average distance: 149.6 milion km
So, we can calculate the percentage change with respect to the average distance as:
$d= \frac{d(aphelion)-d(perihelion)}{d(average)}\cdot 100= \frac{152.1-147.1}{149.6}\cdot 100=3.3 \%$

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A type of Lead (Pb) ion has a + 4 oxidation number. Sulfur (S) has a — 2 oxidation number. What would be the chemical formula fo

serious [3.7K]

Answer: The chemical formula for the compound of these two elements is $PbS_2$

Explanation:

For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.

Here metal lead is having an oxidation state of +4 called as $Pb^{4+}$ cation and sulphur non metal has oxidation state of -2 called as $S^{2-}$ . Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral $PbS_2$

The chemical formula for the compound of these two elements is $PbS_2$

4 0

3 years ago

If one lawn mower causes an 80-dB sound level at a point nearby, four lawnmowers together would cause a sound level of _________

BartSMP [9]

Answer:

The intensity of 4 lawn movers is 86 dB.

Explanation:

Intensity of one lawnmower = 80 dB

Let the intensity is I.

Use the formula of intensity

$dB = 10 log\left ( \frac{I}{Io} \right )\\\\80=10log\left ( \frac{I}{Io} \right )\\\\10^8 = \frac{I}{10^{-12}}\\\\I = 10^{-4} W/m^2$

Now the intensity of 4 lawn movers is

$dB = 10 log\left ( \frac{4I}{Io} \right )\\\\dB=10log\left ( \frac{4\times10^{-4}}{10^{-12}} \right )\\\\dB = 86 dB\\$

3 0

3 years ago

A 70 watt light bulb is run by a 120 v circuit. how many amps does it use

Marizza181 [45]

Current = Power/Voltage. 70W/120v= 0.583 Amps.

6 0

4 years ago

Sally is trying to lift a heavy box, but is not strong enough to lift it. Would the force that she is applying to the box be an

mestny [16]

If you give it unbalanced force it would go up and if you can't give it enough it will stay a balanced force

3 0

3 years ago

Calculate the power of the eye in D when viewing an object 5.70 m away. (Assume the lens-to-retina distance is 2.00 cm. Enter yo

Tems11 [23]

Answer:

Power=50.17dioptre

Power=50.17D

Explanation:

P=1/f = 1/d₀ + 1/d₁

Where d₀ = the eye's lens and the object distance= 5.70m=

d₁= the eye's lens and the image distance= 0.02m

f= focal length of the lense of the eye

We know that the object can be viewed clearly by the person ,then image and lens of the eye's distance needs to be equal with the retinal and the eye lens distance and this distance is given as 0.02m

Therefore, we can calculate the power using above formula

P= 1/5.70 + 1/0.02

Power=50.17dioptre

Therefore, the power the eye's is using to see the object from distance is 5.70D

3 0

4 years ago