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2 years ago

Why does the skateboarder continue to move forward when he hits the trash?

2 answers:

7 0

An object at rest stays at rest and an object in motion stays in motion. Or Newtons first law of motion.

lisov135 [29]2 years ago

5 0

Answer:

According to Newton's first law: An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

There is a force that moves the skater and his skate forward, after the hit, his speed is reduced, but this force is not completely counteracted, and that's why he continues moving forward.

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Why is the atomic mass of most elements not a whole number?

Crank

The atomic mass is the average of the isotopes of the element meaning most averages of isotopes will not be whole numbers

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3 years ago

Why do ionic compounds have high melting points?

Vika [28.1K]

These oppositely charged compounds are strongly held by electrostatic forces of attraction as these be together for a long time the rise in temparature occurs so that the the melting points rises in them.

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3 years ago

An iron block of mass 18 kg is heated from 285 K to 318 K. If 267.3 kJ is required, what is the specific heat of iron? A. 450.00

valkas [14]

Answer:

Option A. 450.00

Explanation:

1) Data:

a) m = 18 kg

b) T₁ = 285 K

c) T₂ = 318 K

d) Q = 267.3 kJ

e) S = ?

2) Principles and equations

The specific heat of a substance is the amount of heat energy absorbed to increase the temperature of certain amount (gram, kg, or moles, depending on the definition or units) of the substance in 1 ° C or 1 K.

The mathematical relation between the specific heat and the heat energy absorbed is:

Q = m × S × ΔT

Where,

Q is the heat absorbed,
S is the specific heat, and
ΔT is the temperature increase (T₂ - T₁)

3) Solution:

a) Substitute the data into the equation:

267.3 kJ = 18 kg × S × (318 K - 285 K)

b) Solve for S and compute:

S = 267.3 kJ / (18 kg × 33 K) = 0.45 kJ / (Kg . K)

The options have not units, but I notice that the first answer is 1,000 times the answer I obtained, so I will make a conversion of units.

c) Convert to J /( kg . k):

0.45 kJ / (Kg . K) × 1,000 J / kJ = 450 J / (kg . K)

Now we can see that the option A is is the answer, assuming the units.

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3 years ago

The Geocentric and the Heliocentric models are descriptions of the universe known at the time when these models were developed.

RSB [31]

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Explanation:I answerd the question before in Earth Science

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2 years ago

What percentage of the mass of hydrofluoric acid (HF) is contributed by hydrogen?

Morgarella [4.7K]

This problem is asking for the percent by mass of hydrogen in hydrofluoric acid. At the end, the answer turns out to be D. 5% as shown below:

<h3>Percent compositions:</h3>

In chemistry, percent compositions are used for us to know the relative amount of a specific element in a compound. In order to do so for hydrogen, we use the following formula, which can also be applied to any other element in a given compound:

$\% H=\frac{m_H*1}{M_{HF}}*100\%$

Where $m_H$ stands for the atomic mass of hydrogen and $M_{HF}$ for the molar mass of hydrofluoric acid. In such a way, we plug in the atomic masses of hydrogen (1.01 g/mol) and fluorine (19.0 g/mol) to obtain:

$\% H=\frac{1.01g/mol*1}{1.01g/mol+19.0g/mol}*100\%\\\\\% H=5\%$

Learn more about percent compositions: brainly.com/question/12247957

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2 years ago