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3 years ago

Explain the differences between a physical and chemical change, and give examples of each.

1 answer:

4 0

Chemical change: a reaction/event where the chemicals/elements present before the change are NOT the same molecules present after the change.
For example, combustion reactions such as the burning of wood or rubbing alcohol are examples of chemical change. The reactants before the combustion of rubbing alcohol are CH3O (rubbing alcohol) and O2 oxygen (oxygen). The molecules present after the combustion reaction are CO2 (carbon dioxide) and H2O (water vapor).

Physical Change: a change in structure or state of a substance but, after the change the material is the same material that we started with. One example would be breaking a glass bottle by dropping it. The glass is now in smaller pieces than when we started, but the glass molecules are still glass molecules.

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Hooke's law describes a certain light spring of unstretched length 34.8 cm. When one end is attached to the top of a doorframe a

DaniilM [7]

Answer:

a) $k = 1343.6\,\frac{N}{m}$ , b) $l = 0.501\,m\,(50.1\,cm)$

Explanation:

a) The Hooke's law states that spring force is directly proportional to change in length. That is to say:

$F \propto \Delta l$

In this case, the force is equal to the weight of the object:

$F = m\cdot g$

$F = (8.22\,kg)\cdot (9.807\,\frac{m}{s^{2}} )$

$F = 80.614\,N$

The spring constant is:

$k = \frac{F}{\Delta l}$

$k = \frac{80.614\,N}{0.408\,m-0.348\,m}$

$k = 1343.6\,\frac{N}{m}$

b) The length of the spring is:

$F = k\cdot (l-l_{o})$

$l = l_{o} + \frac{F}{k}$

$l=0.348\,m+\frac{205\,N}{1343.6\,\frac{N}{m} }$

$l = 0.501\,m\,(50.1\,cm)$

6 0

3 years ago

HELP. A river flows South with a speed of 8m/s. From the shore, you see a boat moving South with a speed of 10 m/s. From their f

riadik2000 [5.3K]

Answer:

18 m/s

Explanation:

Given that,

Speed of river is 8 m/s due South

From the shore, you see a boat moving South with a speed of 10 m/s. Both boat and river are moving in same direction. The resultant velocity will add up.

v = 10 m/s + 8 m/s

v = 18 m/s

Hence, the rowers are moving with a speed of 18 m/s.

3 0

2 years ago

Plants make food through photosynthesis, a chemical reaction. What are the starting substances of the reaction?

vekshin1

The answer is the 4th option because they don't use oxygen, that's what they produce

3 0

3 years ago

Read 2 more answers

The ocean’s tides are not only affected by the shape of the coastlines, or slope of the ocean floor, but also by the gravitation

dexar [7]

Answer:

a) According to Newton's law of gravitation, as the distance between the Moon and the Earth decreases, the gravitational attraction increases and vice versa

The gravitational force of the Moon on the Earth causes the Earth to be slightly bulged on the side directly facing the Moon

The gravitational force also pulls the water bodies on the Earth's surface towards the Moon in the same manner and the effect is more pronounced due to the ability of the liquid water to assume a shape based on the magnitude of the gravitational field attracting it

Therefore, the region where the Moon is closest to the Earth we have a high tide as the water level rises and the region which is perpendicular to where the Moon is located has a low tide

b) The two special types of tides are

1) The neap tide

2) The spring tide

Neap tide

Neap tide occurs when the Sun and Moon are 90° apart from each other when they are viewed by an observer from Earth

The gravitational pull of the Sun cancels (partially) the effect of the gravitational pull and tidal force of the Moon, resulting in minimum tidal range

Spring Tide

Spring tide occurs when the Earth, the Moon, and the Sun are simultaneously inline, such that the Sun reinforces the gravitational pull and tidal force of the Moon, resulting in a maximum tidal range

Explanation:

4 0

2 years ago

Read 2 more answers

If you wanted to live where the chances of a destructive earthquake were small, would you pick a location near a fault zone, nea

exis [7]

Answer: A volcanic island arc like Hawaii.

Explanation: The Hawaiian island is the most safest place for the people to live in comparison to the other given options.

The plate tectonic movement generates energy due to collision, resulting in sudden release of energy, and seismic waves are produced that propagates and causes earthquake.

Due to the constant collision between the plates, different places at different time experiences earthquake. Near a fault region, earthquakes are very severe, and also near the mid oceanic ridge it is not possible for a person to live. The subduction zones are the region where a denser plate subducts beneath the other, and its impossible for life to exist there.

Thus the most safest place out of all the option is the volcanic islands where numerous people resides. for example, the Hawaiian and Stromboli.

5 0

3 years ago