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KiRa [710]
2 years ago
6

True or false A clue that a chemical change had occurred is that heat is given off.

Physics
2 answers:
maxonik [38]2 years ago
8 0
True


A chemical change has probably occurred if bubbles are released, there is a change of color, or an odor is produced. Other clues include the release of heat, light, or loud sounds.
oksian1 [2.3K]2 years ago
4 0

Answer:

true

Explanation:

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3 years ago
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A block–spring system vibrating on a frictionless, horizontal surface with an amplitude of 7.0 cm has an energy of 14 J. If the
Bingel [31]

Answer:

E_T= 28J

Explanation:

The energy of Mass-Spring System the sum of the potential energy of the block plus the kinetic energy of the block:

E_T=U+K=\frac{1}{2} k \Delta x^2+\frac{1}{2} mv^2

Where:

\Delta x=Amplitude\hspace{3}or\hspace{3}d eformation\hspace{3} of\hspace{3} the\hspace{3} spring\\m=Mass\hspace{3}of\hspace{3}the\hspace{3}block\\k=Constant\hspace{3}of\hspace{3}the\hspace{3}spring\\v=Velocity\hspace{3}of\hspace{3}the\hspace{3}block

There are two cases, the first case is when the spring is compressed to its maximum value, in this case the value of the kinetic energy is zero, since there is no speed, so:

E_T=\frac{1}{2} k \Delta x^2\\\\14=\frac{1}{2} k7^2\\\\Solving\hspace{3} for\hspace{3} k\\\\k=\frac{28}{49} =\frac{4}{7}

The second case is when the block passes through its equilibrium position, in this case the elastic potential energy is zero since \Delta x=0, so:

E_T=\frac{1}{2} mv^2\\\\14=\frac{1}{2} mv^2\\\\Solving\hspace{3} for\hspace{3} v\\\\v^2=\frac{28}{m}

Now, let's find the energy of the system when the block is replaced by one whose mass is twice the mass of the original block using the previous data:

E_T=U+K=\frac{1}{2} k \Delta x^2+\frac{1}{2} m_2v^2

Where in this case:

m_2=New\hspace{3}mass=Twice\hspace{3} the\hspace{3} mass \hspace{3}of\hspace{3} the\hspace{3} original=2m

Therefore:

E_T=\frac{1}{2} (\frac{4}{7} ) (7^2)+\frac{1}{2} (2m)(\frac{28}{m_2})=\frac{1}{2} (\frac{4}{7} ) (7^2)+\frac{1}{2} (2m)(\frac{28}{2m})=14+14=28J

8 0
3 years ago
How does electrical conduction compare between metals, nonmetals, and metalloids
zhuklara [117]

Answer:

metal> metalloids >nonmetals    (Electrical conductivity)

Explanation:

Electrical conductivity of objects can be compared by the bonding energy of electrons in them.

Metals have less bonding energy of electrons, so even at room temperature their are significant number of free electrons to carry electrical current.

Nonmetals have a very high bonding energy of electrons, so  at room temperature negligible number of free electrons are present so electrical conductivity is very low.

Metalloids have both metallic and non metallic features. The electron bonding energy falls in between that of metals and nonmetals. So electrical conductivity also lies in between metals and nonmetals.

4 0
3 years ago
The most important part of physical fitness is. Strength. B muscular endurance c flexibility. D. Cardiovascular
solniwko [45]
The answer is D. Cardiovascular
7 0
3 years ago
How many 100W light bulbs could be powered for one year by the direct conversion of 1g of matter into energy?
stellarik [79]

Answer:

No. of 100 W bulbs, n = 28,539 bulbs

Given:

Power of a single bulb = 100 W

Time period, T = 1 yr = 365\times 24\times 60\times 60 = 31,536,000 s

mass of matter, m = 1 g = 1\times 10^{-3}]

Solution:

According to Eintein's mass-energy equivalence:

E = mc^{2}

E = 1\times 10^{-3}\times (3\times 10^{8})^{2}

E =  9\times 10^{13} J

Power of a single bulb, P =  \frac{E}{T}

                                       P =  \frac{9\times 10^{13} }{31,536,000}

                                       P = 28,53,881 W

No. of 100 W bulbs, n = \frac{P}{power of one bulb}

                                 n = \frac{28,53,881}{100}

                                 n = 28,539

5 0
3 years ago
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