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2 years ago

_____ bodies help in reducing friction

Physics

2 answers:

Tju [1.3M]2 years ago

8 0

Explanation:

Friction can be reduced by

Polishing the rough surface.

Oiling or lubricating with graphite or grease the moving parts of a machine

Providing all bearings or wheels between the moving parts of a machine or vehicles reduce friction and allow smooth movement as rolling friction is less than sliding friction.

amm18122 years ago

6 0

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How do magnetic forces repel or attract?

Lerok [7]

“Magnets are surrounded by an invisible magnetic field that is made by the movement of electrons, the subatomic particles that circle the nucleus of an atom”

“Every magnet has both a north and a south pole. When you place the north pole of one magnet near the south pole of another magnet, they are attracted to one another. When you place like poles of two magnets near each other (north to north or south to south), they will repel each other.”

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3 years ago

Select the correct answer.

kipiarov [429]

Answer:

Explanation:

If the object is moving at a constant speed, the object isn't accelerating as the velocity doesn't change.

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3 years ago

It is not just lab chemicals but also common household substances that can be classified as acidic, basic, and neutral materials

Montano1993 [528]

Acidic: coffee, orange juice , soft drink, vinegar

Basic: Antacid, Baking soda, Detergent, Lye, Milk of Magnesia

Neutral: water, Sugar, Table salt.

<u>Explanation:</u>

Acidic substances have high concentration of hydrogen ions and have pH value less than 7. Basic substances have high concentration of hydroxide ions and have pH value more than 7. Neutral substance have pH value 7. The concentration oh hydrogen ions and hydroxide ions is equal.

Salt is formed when a acid reacts with base in a neutralization reaction. Different types of salt are formed depending upon the concentration of hydrogen and hydroxide ions. Neutral salt is formed when concentration of hydrogen ion is equal to concentration of hydroxide ions.

Coffee, orange juice , soft drink, vinegar are acidic substances. Antacid, Baking soda, Detergent, Lye, Milk of Magnesia. water, Sugar, Table salt are neutral substances.

6 0

3 years ago

The concentration of Biochemical Oxygen Demand (BOD) in a river just downstream of a wastewater treatment plant’s effluent pipe

shtirl [24]

Answer:

The BOD concentration 50 km downstream when the velocity of the river is 15 km/day is 63.5 mg/L

Explanation:

Let the initial concentration of the BOD = C₀

Concentration of BOD at any time or point = C

dC/dt = - KC

∫ dC/C = -k ∫ dt

Integrating the left hand side from C₀ to C and the right hand side from 0 to t

In (C/C₀) = -kt + b (b = constant of integration)

At t = 0, C = C₀

In 1 = 0 + b

b = 0

In (C/C₀) = - kt

(C/C₀) = e⁻ᵏᵗ

C = C₀ e⁻ᵏᵗ

C₀ = 75 mg/L

k = 0.05 /day

C = 75 e⁻⁰•⁰⁵ᵗ

So, we need the BOD concentration 50 km downstream when the velocity of the river is 15 km/day

We calculate how many days it takes the river to reach 50 km downstream

Velocity = (displacement/time)

15 = 50/t

t = 50/15 = 3.3333 days

So, we need the C that corresponds to t = 3.3333 days

C = 75 e⁻⁰•⁰⁵ᵗ

0.05 t = 0.05 × 3.333 = 0.167

C = 75 e⁻⁰•¹⁶⁷

C = 63.5 mg/L

5 0

2 years ago

Compare the light gathering power of a 1 meter diameter telescope to that of the human eye ,which has a diameter of roughly 2.5

lesantik [10]

Answer:

The telescope can gather light 1600 times more than the human eyes can!

Explanation:

The light gathering ability of an optical element is directly proportional to its area of opening.

So, in comparing the light gathering abilities for two objects, it is just the ratio of their area of opening.

Let the diameter of the telescope be D = 1 m

And the diameter of the human eyes be d = 2.5 cm = 0.025 m

Light gathering ability of the telescope compared to the eyes = D² ÷ d²

= (D²/d²) = (1²/0.025²) = 1600 times.

The telescope can gather light 1600 times more than the human eyes can!

Hope this Helps!!!

7 0

3 years ago