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Arada [10]
3 years ago
8

Every year _______ species go extinct. a. 3 b. 72 c. 1000 d. 20000

Physics
2 answers:
Tems11 [23]3 years ago
7 0
Well, the thing is: we don't really know, as we don't even know how many species there are on earth.

If we take a look at the estimates of <span>World Wide Fund for Nature, an organization that works toward combating species extinction, their estimates vary from 200 to 100 000 - but a probable number is 20 000 (d). </span>
<span />
schepotkina [342]3 years ago
6 0

Answer:

d. 20000

Explanation:

It has been observed that over the years, species have been going extinct due to human reasons such as excessive hunting, environmental factors such as natural disasters, global warming and also due to changes in their genetic makeup or a reduced reproduction.

It has been estimated that every year 20,000 species are going extinct.

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According to Newton's 3rd Law, an object's momentum depends on it's velocity and mass. 4 dog-sled teams competed to see who coul
podryga [215]

Answer:

C.) Sled Team C 28 kg moving at 12m/s

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3 years ago
Consider a compact car that is being driven
aliina [53]

Answer:

Height h = 37.8 m

Explanation:

Given :

Velocity of car (v) = 98 km / h

Acceleration of gravity = 9.8 m/s²

Computation:

Acceleration of gravity = 9.8 m/s²

Acceleration of gravity = (98)(1,000 m / 3,600 s)

Acceleration of gravity = 27.22 m/s

By using law of conservation of energy ;

(1/2)mv² = mgh

h = v² / 2g

h = 27.22² / 2(9.8)

Height h = 37.8 m

5 0
3 years ago
Identifying Characteristics Common to All Protists Use the drop-down menus to complete the statements. All protists live in envi
Annette [7]

Answer:

Use the drop-down menus to complete the statements.

All protists live in environments that are

✔ wet

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All protists must

✔ reproduce

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All protists have

✔ a nucleus

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All protists make or consume

✔ food

Explanation:

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3 0
3 years ago
Read 2 more answers
A person's _____________ will change if they move from the Earth to the moon.
Diano4ka-milaya [45]

1. A person's weight will change if they move from the Earth to the moon.

In fact, the weight of a person is given by:

W=mg

where m is the mass of the person and g is the gravitational acceleration. The mass of the person, m, is the same on the Earth and on the moon, but the value of g is different on the Moon (about 1/6 of the Earth's value), so the weight also changes.


2. An astronaut is launched into space. The mass of the astronaut did not change. This is measured in Kg.

The mass of an object (or of a person, as in this case) is an intrinsec property of the object, that depends on the amount of matter inside the object: therefore, this quantity does not depend on the location of the object, so it is the same on the Earth, on the Moon and in space.


3. What is the weight of a ring tailed lemur that has a mass of 10 kg? -98 N

The weight of the lemur is given by:

W=mg

where m=10 kg is the lemur's mass and g=-9.8 m/s^2 is the gravitational acceleration. Using these numbers, we find

W=(10 kg)(-9.8 m/s^2)=-98 N

and the negative sign simply means that the direction of the weight is downward.


4. What is the mass of the lemur from the previous question if it was on the International Space Station? 10 kg

As we said in question 1), the mass of an object does not depend on the location, so the mass of the lemur is still 10 kg, as in the previous exercise.


5. A rocket being thrust upward as the force of the fuel being burned pushes downward is an example of which of Newton's laws? Third's Newton Law

Third's Newton Law states that:

"When an object A exerts a force on an object B, then object B exerts an equal and opposite force on object A".

Applied to this case, the two objects are the fuel and the rocket. The fuel is pushed backward by the rocket, so the fuel exerts an equal and opposite force on the rocket, which then moves forward.


6. When a cannon is fired, the projectile moves forward. According to Newton's 3rd law, the cannon will want to travel backward.

Third's Newton Law states that:

"When an object A exerts a force on an object B, then object B exerts an equal and opposite force on object A".

Applied to this case, the two objects are the cannon and the projectile.The projectile is pushed forward by the cannon, so the projectile exerts an equal and opposite force on the cannon, which moves backward.


7. An object has a weight of 21,532 N on Earth. What is the mass of the object? 2,197 kg

The weight of the object is given by: W=mg

If we re-arrange the formula and we use W=21,532 N, we can find the mass of the object:

m=\frac{W}{g}=\frac{21,532 N}{9.8 m/s^2}=2,197 kg


8. What is the mass of the object from the previous question if we put it on the moon? The force of gravity on the moon is 1.62 m/s2.  2,197 kg

As we said in question 4), the mass of an object does not change if we move it to another location, so its mass is still 2,197 kg.


9. How much force is exerted if a 250 kg object has an acceleration of 750 m/s2 ? 187,500 N

The force exerted on the object is given by Newton's second law:

F=ma

where F is the force, m=250 kg is the mass and a=750 m/s^2 is the acceleration. By using these numbers, we find

F=(250 kg)(750 m/s^2)=187,500 N


10. A resting soccer ball moving after it is kicked is an example of which of Newton's laws? Newton's second law

Newton's second law states that when an object is acted upon unbalanced force, the object has an acceleration, given by the law

F=ma

So, in this case, the ball is kicked and so an unbalanced force is applied to it, and for this reason the ball has an acceleration (in fact, it starts from rest, but then its velocity increases since it starts moving).

5 0
3 years ago
19. Explain why a magnet from your refrigerator could not be used to lift something as heavy as a car. (Chapter 7 – Pages 202-20
tangare [24]

19. Answer:

It is because the gravitational force of Earth on a car is much more than the magnetic force from a refrigerator magnet. The gravitational force of earth on an object is directly proportional to the mass of the object. Due to the large mass of the car. the gravitational force on it is much greater and a refrigerator magnet cannot be used to lift the car.

20. Answer:

No, a magnet can never have a single pole. When cut in half, it develops two poles again

This is explained by Gauss's law of magnetism according to which the divergence of magnetic field is zero. The magnetic field lines must form a closed loop. In order to form a balanced closed loop, a magnet must have two poles.

21. Answer:

If the frequency of a wave is increased, the wavelength decreases.

Let us assume a wave with velocity v and wavelength λ is moving with a frequency f. We know that the velocity of a wave is always constant and is given as:

v = fλ

or λ=v/f

the relationship between λ and f is given as:

λ ∝ 1/f

When frequency is increased, the wavelength decreases.

22. Answer:

Wavelength of an ocean wave = λ = 10 m

Frequency of the ocean wave = f = 4.0 Hz

Velocity of the wave = v = ?

We know that for a wave with wavelength λ and frequency f, the velocity of that wave is given by the formula:

                             v = fλ

Using the given values in the formula:

v = (4 Hz)(10 m)

v = (4 s⁻¹)(10 m)                     (f = 1/T and Hz = s⁻¹)

v = 40 ms⁻¹

23. Answer:

If the sound of a siren becomes lower in pitch, it means that the vehicle is moving away from you. This is because of Doppler's effect.

According to Doppler's effect, when the source is moving away from a stationary receiver, the wavelength of the wave increases and thus the frequency f of the wave decreases to frequency f'.

f' = f(V/(V + Vs)         (V = velocity of wave ;   Vs = Velocity of source)

24. Answer:

Two astronauts in space are unable to hear each other. This is because sound waves cannot travel in space.

Sound waves are longitudinal waves. They need a medium to travel. Sound travels to our year by vibrating through the air molecules. In deep space, there are no molecules to vibrate. So there is no sound.

25. Answer:

Electromagnetic waves can transfer energy through vacuum.

EM waves are produced from an oscillating charged particles. It contains electric field waves and magnetic field waves oscillating perpendicular to each other. The plane of propagation of EM wave is in a plane perpendicular to both of them.

Once in motion, EM waves are self-perpetuating. Change is one field produces the other and so on.

26. Answer:

Three types of electromagnetic waves:

Ultraviolet rays:

Waves that have wavelength just shorter than the visible rays. Example is the UV radiations from the sun that cause sunburns.

X-rays:

X-rays have wavelength even shorter than UV radiations. Example: X-rays are used to take pictures of bones. They can penetrate through skin and muscles.

Gamma rays:

Gamma rays are the shortest waves and have the most energy. Example: Gamma rays used in treating cancer.

27. Answer:

A leaf usually appears to be green because chlorophyll absorbs light in the red and the blue regions of the visible light spectrum. Green light is not absorbed but reflected, making the plant appear green. Similarly, A red flower appears red because it reflects wavelengths most strongly in the red part of the spectrum. Light in the other range is absorbed.

28. Answer:

Light waves have different speed in different mediums.

On reflection, it remains in the same medium. So the speed of light also remains constant.

In refraction, the medium changes and the speed changes as well. Light is slower in denser mediums. Velocity of the light wave will decrease in a denser medium. To keep frequency constant, the wavelength of the wave will also shorten.

29. Answer:

A Convex lens converges the light rays towards the principal axis. Where as a Concave lens diverges the light rays away from the principal axes.

Convex lens is thicker at the center while Concave lens is thinner at the center.

Convex lens has a positive focal length while the concave lens has a negative focal length.

30. Answer:

The mirror used in rear-view mirror of a car are slightly curved (convex mirror).

The mirror is curved in an attempt to eliminate blind spots for the driver, making it safer and easier to view objects on the back of the vehicle.

The warning, "Objects in mirror are closer than they appear." is important because it is true. The image formed by a convex mirror is far than that of the actual objects. So, the driver is warned.

6 0
2 years ago
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