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o-na [289]
3 years ago
12

About three billion years ago, single-celled organisms called cyanobacteria lived in Earth’s oceans. They thrived on the ocean’s

abundance of ___ , which they used during the process of photosynthesis. Much later, this process allowed organisms, such as fish, to survive by extracting dissolved ___ from ocean waters.
a. oxygen
b.carbon dioxide
c. nitrogen
Physics
2 answers:
quester [9]3 years ago
6 0

The first blank is carbon dioxide, second one is oxygen

pickupchik [31]3 years ago
3 0
I think its Oxygen. 
ancient cyanobacteria produced Earth's first oxygen-rich atmosphere, which allowed the eventual rise of eukaryotes. T<span>he chloroplasts of eukaryotic algae and plants are derived from cyanobacteria</span>
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They both have a certain force. They are different because that force is different
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31) The basic concept of how a simple motor works is explained by which statement?
Firdavs [7]

Answer:

When a wire that carries electrical current is placed in a magnetic field the wire experiences a force.

Explanation:

The electric motor is a device which convert electrical energy into mechanical energy  ie when current carrying conductor is placed in magnetic field it experience a force. Flemings left hand rule explains the direction of the current.

The electric motor works by attraction and repulsion of magnetic field.

So the option d explains basic concept of simple motor ie when when current carrying wire is placed in the magnetic field it experience magnetic repulsive force.

5 0
3 years ago
An astronomer observes an asteroid in the solar system. He notes that the asteroid is three times farther from the Sun than Eart
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3 0
3 years ago
Read 2 more answers
A particle makes 800 revolution in 4 minutes of a circle of 5cm. Find
vladimir1956 [14]

Answer:

i) The period of the particle is 0.3 seconds

ii) The angular velocity is approximately 20.94 rad/s

iii) The linear velocity is approximately 1.047 m/s

iv) The centripetal acceleration is approximately 6.98 m/s²

Explanation:

The given parameters are;

The number of revolution of the particle, n = 800 revolution

The time it takes the particle to make 800 revolutions = 4 minutes

The dimension of the circle = 5 cm = 0.05 m

Given that the dimension of the circle is the radius of the circle, we have;

i) The period of the particle, T = The time to complete one revolution

T = 1/(The number of revolutions per second)

∴ T = 1/(800 rev/(4 min × 60 s/min)) = 3/10 s

The period, T = 3/10 seconds = 0.3 seconds

ii) The angular velocity, ω = Angle covered/(Time)

800 revolutions in 4 minutes = Angle of (800 × 2·π) in 4 minutes

∴ ω = (800 × 2·π)/(4 × 60) = 20·π/3

The angular velocity, ω = 20·π/3 rad/s ≈ 20.94 rad/s

iii) The linear velocity, v = r × ω

∴ The linear velocity, v = 0.05 m × 20·π/3 rad/s = π/3 m/s ≈ 1.047 m/s

iv) The centripetal acceleration, a_c = v²/r

∴ The centripetal acceleration, a_c = (π/3)²/(0.05) = 20·π/9

The centripetal acceleration, a_c = 20·π/9 m/s² ≈ 6.98 m/s²

4 0
2 years ago
A Hall probe, consisting of a rectangular slab of current-carrying material, is calibrated by placing it in a known magnetic fie
Citrus2011 [14]

Answer:

(a) 0.345 T

(b) 0.389 T

Solution:

As per the question:

Hall emf, V_{Hall} = 20\ mV = 0.02\ V

Magnetic Field, B = 0.10 T

Hall emf, V'_{Hall} = 69\ mV = 0.069\ V

Now,

Drift velocity, v_{d} = \frac{V_{Hall}}{B}

v_{d} = \frac{0.02}{0.10} = 0.2\ m/s

Now, the expression for the electric field is given by:

E_{Hall} = Bv_{d}sin\theta                            (1)

And

E_{Hall} = V_{Hall}d

Thus eqn (1) becomes

V_{Hall}d = dBv_{d}sin\theta

where

d = distance

B = \frac{V_{Hall}}{v_{d}sin\theta}                      (2)

(a) When \theta = 90^{\circ}

B = \frac{0.069}{0.2\times sin90} = 0.345\ T

(b) When \theta = 60^{\circ}

B = \frac{0.069}{0.2\times sin60} = 0.398\ T

5 0
3 years ago
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