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3 years ago

5

A change of color is a sign that a chemical reaction is taking place. true or false

1 answer:

Citrus2011 [14]3 years ago

3 0

That is true. Change in color, formation of a precipitate, and production of gas are the three chemical changes.

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The frequency of light emitted from a source is changed. What visible evidence would indicate this?

Llana [10]

The change of color. Each color has a different wavelength therefore a different frequency.

5 0

3 years ago

Read 2 more answers

At present most of the world's energy needs are supplied by what kind of energy

antiseptic1488 [7]

Fossil fuels . . . coal, oil, natural gas

Among primitive cultures, wood is an important source.

4 0

3 years ago

If the action force is the swimmer pushing water in the leftward direction, what is the reaction force?

Sphinxa [80]

According to Newton's Third Law of Motion, to every action, there is an equal and opposite reaction; action and reaction act on different bodies.
Here, the action force is in the leftward direction, so the reaction will be in the opposite direction.
If the action force is the swimmer pushing water in the leftward direction, then the reaction force is in the rightward direction.
And the reaction force will be given by the water on the swimmer.

<u>Answer</u><u>:</u>

<u>The </u><u>reaction </u><u>force </u><u>is </u><u>the </u><u>water </u><u>pushing </u><u>the </u><u>swimmer </u><u>in </u><u>the </u><u>rightward </u><u>direction</u><u>.</u>

Hope you could get an idea from here.

Doubt clarification - use comment section.

3 0

2 years ago

An initially uncharged 3.47-μF capacitor and a 6.43-kΩ resistor are connected in series to a 1.50-V battery that has negligible

harkovskaia [24]

Answer: a) io=233.28 A ( initial current); b) τ=R*C= 22.31 ms; c) 81.7 ms

Explanation: In order to explain this problem we have to use, the formule for the variation of the current in a RC circuit:

I(t)=io*Exp(-t/τ)

and also we consider that io=V/R=(1.5/6.43*10^3)

=233.28 A

then the time constant for the RC circuit is τ=R*C=6.43*10^3*3.47*10^-6

=22.31 ms

Finally the time to reduce the current to 2.57% of its initial value is obtained from:

I(t)=io*Exp(-t/τ) for I(t)/io=0.0257=Exp(-t/τ) then

ln(0.0257)*τ =-t

t=-ln(0.0257)*τ=81.68 ms

3 0

3 years ago

Two particles, each of mass m, are initially at rest very far apart.Obtain an expression for their relative speed of approach at

PSYCHO15rus [73]

Answer:

$|\Delta v |=\sqrt{\frac{4Gm}{d} }$

Explanation:

Consider two particles are initially at rest.

Therefore,

the kinetic energy of the particles is zero.

That initial K.E. = 0

The relative velocity with which both the particles are approaching each other is Δv and their reduced masses are

$\mu= \frac{m_1m_2}{m_1+m_2}$

now, since both the masses have mass m

therefore,

$\mu= \frac{m^2}{2m}$

= m/2

The final K.E. of the particles is

$KE_{final}=\frac{1}{2}\times \mu\times \Delta v^2$

Distance between two particles is d and the gravitational potential energy between them is given by

$PE_{Gravitational}= \frac{Gmm}{d}$

By law of conservation of energy we have

$KE_{initial}+KE_{final}= PE_{gravitaional}$

Now plugging the values we get

$0+\frac{1}{2}\frac{m}{2}\Delta v^2= -\frac{Gmm}{d}$

$|\Delta v |=\sqrt{\frac{4Gm}{d} }$

$=\sqrt{\frac{Gm}{d} }$

This the required relation between G,m and d

5 0

3 years ago