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leva [86]
3 years ago
12

1. To describe the length of a classroom, a student should use what? A) centigrams B) centimeters C) kilometers D) meters 2. Whi

ch is a standard metric base unit, correctly matched with what it measures?
A) Kelvin: time B) second: time C) meter: volume D) gram: temperature A tectonic plate near Niihau, an island in Hawaii, grows at an average rate of 11 cm/year. How many centimeters will the plate grow in 2 years?
A) 2 cm B) 11 cm C) 22 cm D) 30 cm The plate near the Artic Ridge is among those with the slower growth rates, moving slightly less than 2.5 cm/year. How much will the plate move in 10 years? A) less than 5 cm B) equal to 25 cm C) less than 25 cm D) greater than 25 cm
Physics
2 answers:
Gemiola [76]3 years ago
7 0
1).  To describe the length of a classroom, a student can use any unit
he feels like using.  Some units will produce ridiculous numbers, though. 
The most convenient numbers will result from using meters or centimeters. 
If the room is, say, 20 feet long, then that's about 0.0061 kilometer, or
about 610 centimeters, or about 6.1 meters.
Meters is probably best.

2).
A). Kelvin: time.       No.  Kelvin is a unit of temperature.
B). second: time    Yes.  Second is a unit of time.
C). meter: volume    No.  Meter is a unit of length or distance.
D). gram: temperature.  No.  Gram is a unit of mass.

3).  A plate near Hawaii grows about 11 cm per year.
So it grows 11 cm in the first year, and another 11 cm in the second year.
The total growth in 2 years is (11cm + 11cm) = 22 cm .

4).  A slower plate in the Arctic moves slightly less than 2.5 cm per year.
It moves ...
slightly less than 2.5 cm in the 1st year
slightly less than 2.5 cm in the 2nd year
slightly less than 2.5 cm in the 3rd year
slightly less than 2.5 cm in the 4th year
slightly less than 2.5 cm in the 5th year
slightly less than 2.5 cm in the 6th year
slightly less than 2.5 cm in the 7th year
slightly less than 2.5 cm in the 8th year
slightly less than 2.5 cm in the 9th year
and
slightly less than 2.5 cm in the 10th year
for a grand total of 
           (slightly less than 2.5 cm x 10) = less than 25 cm in 10 years.

sdas [7]3 years ago
7 0

1 d,   2 b,   3 c,   4 c that is the answer to them

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A ceiling fan with 90-cm-diameter blades is turning at 64 rpm . Suppose the fan coasts to a stop 28 s after being turned off. Wh
mixas84 [53]

Answer:

the speed of the tip of a blade 10 s after the fan is turned off is 16.889 m/s.

Explanation:

Given;

diameter of the ceiling fan, d = 90 cm = 0.9 m

angular speed of the fan, ω = 64 rpm

time taken for the fan to stop, t = 28 s

The distance traveled by the ceiling fan when it comes to a stop is calculated as;

d = vt = \omega r\times  t= ( \frac{64 \ rev}{\min} \times \frac{2 \pi \ rad}{rev} \times \frac{1 \min}{60 \ s} \times 0.9 \ m) \times 28 \ s\\\\d = 168.89 \ m

The speed of the tip of a blade 10 s after the fan is turned off is calculated as;

v = \frac{d}{t} \\\\v = \frac{168.89}{10} \\\\v = 16.889 \ m/s

Therefore, the speed of the tip of a blade 10 s after the fan is turned off is 16.889 m/s.

4 0
3 years ago
Convert 3402kgm/s to 20000Newtons
oee [108]

The 3,402 has units of kg-m/s.  That's momentum.  The 20,000 has units of Newtons.  That's force.  Momentum and force are different physical things, and you can't convert them from one to the other.

The best I can do for you is something like this:

Let's say you have a moving object with 3,402 kg-m/s of momentum, and you want to STOP it completely.  You want to stand in front of it and push back on it, hard enough and for long enough to CHANGE its momentum from 3,402 kg-m/s to zero.

Also ... there's a limit to how hard you can push.  The most force you can exert is 20,000 Newtons.

The amount you'll change its momentum is called the <u><em>impulse</em></u> you give it.  The quantity of impulse is (force) x (length of time you push on it).

So you need to keep pushing it back for (T seconds) long enough so that

(20,000 Newtons of force) x (T seconds) = 3,402 kg-m/s of momentum .

Divide each side of that equation by (20,000 Newtons). Then it says:

(T seconds) = (3,402 kg-m/s) / (20,000 Newtons)

<em>T = 0.1701 second</em>

And that's how you provide just enough impulse to stop the flying object ... push on it with 20,000 Newtons of force for exactly 0.1701 second, and it loses all its momentum and falls out of the air onto the ground at your feet.

This story is the closest I can come to anything that looks like "convert"ing momentum into force.

3 0
3 years ago
A mobile starts with a speed of 250m / s and begins to decelerate at a rate of 3m / s². How fast is it after 45s?
Korvikt [17]

\large{ \underline{ \underline{ \bf{ \purple{Given}}}}}

  • Speed of the mobile = 250 m/s
  • It starts decelerating at a rate of 3 m/s²
  • Time travelled = 45s

\large{ \underline{ \underline{ \bf{ \green{To \: find}}}}}

  • Velocity of mobile after 45 seconds

\large{ \underline{ \underline{ \red{ \bf{Now, \: What \: to \: do?}}}}}

We can solve the above question using the three equations of motion which are:-

  • v = u + at
  • s = ut + 1/2 at²
  • v² = u² + 2as

So, Here a is acceleration of the body, u is the initial velocity, v is the final velocity, t is the time taken and s is the displacement of the body.

\large{ \bf{ \underline{ \underline{ \orange{Solution:}}}}}

We are provided with,

  • u = 250 m/s
  • a = -3 m/s²
  • t = 45 s

By using 1st equation of motion,

⇛ v = u + at

⇛ v = 250 + (-3)45

⇛ v = 250 - 135 m/s

⇛ v = 115 m/s

✤ <u>Final</u><u> </u><u>velocity</u><u> </u><u>of</u><u> </u><u>mobile</u><u> </u><u>=</u><u> </u><u>1</u><u>1</u><u>5</u><u> </u><u>m</u><u>/</u><u>s</u>

<u>━━━━━━━━━━━━━━━━━━━━</u>

4 0
3 years ago
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lyudmila [28]

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5 0
3 years ago
Match each property with the benefit it provides to people on Earth. A. magnetic field filters cancer-causing rays from the sun
vodomira [7]

The correct matching are the following:

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  • C. carbon dioxide: retains heat energy from the sun in the atmosphere
  • D. water in oceans, lakes, rivers and streams: moderates changes in temperature on the surface

The electromagnetic field of the Earth protects us from solar wind by deflecting it. Without it, the charged particles would strip away our ozone, which will lead to the end of life on Earth.

The ozone is a layer in the stratosphere that filters the suns rays. It filters the UV rays by absorbing it. This prevents the UV rays from damaging the surface of the Earth.

Carbon dioxide retains heat in the atmosphere, which creates a greenhouse effect. It is beneficial for us, but because human activity like industrial activities emit so much carbon in the atmosphere that it ends up being harmful.

Bodies of water found on Earth regulate the temperature of the Earth through ocean currents. It brings in both cold and warm air to land which also affect precipitation.

Long explanation, I know, but maybe this will help you out in the long run. Good Luck!

3 0
3 years ago
Read 2 more answers
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