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2 years ago

Why do stars twinkle

1 answer:

4 0

As light from a star races through our atmosphere, it bounces and bumps through the different layers, bending the light before you see it. Since the hot and cold layers of air keep moving, the bending of the light changes too, which causes the star's appearance to wobble or twinkle.

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The activation energy of a reaction going on its own is 20 kj. If the reaction was treated with a catalyst, which would most lik

storchak [24]

Answer:

15 kJ

Explanation:

We need to know the following;

what is activation energy?

Activation energy is the minimum energy required by reactants for a chemical reaction to take place.

What are catalysts?

Catalysts are molecules or substances that speed up the rate of a chemical reaction.

In other words, catalysts increase the speed at which products are formed from reactants.

How do catalysts speed up reactions?

Catalysts speed the rate of chemical reactions by lowering the activation energy of the reactants.
When activation energy is lowered, reactants require less energy for the reaction to occur which easily achieved making the reaction proceed faster.
Therefore, in presence of a catalyst, the new activation energy should be lower than the initial value of activation energy.

7 0

2 years ago

Read 2 more answers

When the Moon orbits Earth, what is the centripetal force?

Troyanec [42]

Answer:

Explanation:

pls mark brainliest

7 0

2 years ago

What is the relationship between pho Thanh energy and the color of light

AysviL [449]

Answer:

Red photons have the least amount of energy

Explanation:

The relationship between the photon energy and the color of light is given by:

$E=\frac{hc}{\lambda}$

where

E is the energy

h is the Planck constant

c is the speed of light

$\lambda$ is the wavelength (which determines the color of light)

As we see from the equation, energy and wavelength are inversely proportional: this means that the longer the wavelength, the lower the energy, and viceversa.

Among the colors in the visible light spectrum, red is the color with longest wavelength (620-750 nm) and violet is the color with shortest wavelength (380-450 nm). This means that red photons have the least amount of energy, while violet photons have the greatest amount of energy.

So the correct choice is

Red photons have the least amount of energy

8 0

2 years ago

An airplane of mass 1.60 ✕ 104 kg is moving at 66.0 m/s. The pilot then increases the engine's thrust to 7.70 ✕ 104 N. The resis

Ivan

(a) No, because the mechanical energy is not conserved

Explanation:

The work-energy theorem states that the work done by the engine on the airplane is equal to the gain in kinetic energy of the plane:

$W=\Delta K$ (1)

However, this theorem is only valid if there are no non-conservative forces acting on the plane. However, in this case there is air resistance acting on the plane: this means that the work-energy theorem is no longer valid, because the mechanical energy is not conserved.

Therefore, eq. (1) can be rewritten as

$W=\Delta K + E_{lost}$

which means that the work done by the engine (W) is used partially to increase the kinetic energy of the airplane ( $\Delta K$ ) and part is lost because of the air resistance ( $E_{lost}$ ).

(b) 77.8 m/s

First of all, we need to calculate the net force acting on the plane, which is equal to the difference between the thrust force and the air resistance:

$F=7.70\cdot 10^4 N - 5.00 \cdot 10^4 N=2.70\cdot 10^4 N$