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3 years ago

Humans first appeared during the _____.

2 answers:

8 0

<span>Humans first appeared during the Quaternary period. <span>The Quaternary or Neozoic period develops in the Cenozoic era, which extends from 2,588 million years ago to the present. The Quaternary is divided into two periods. The Pleistocene, the first and longest period of the period, was characterized by the cycles of glaciations and the appearance of the first humans (homos habilis); this period extended from 2,588 million years to 10,000 years BC The Holocene, the second epoch of the period, was characterized by the end of the glaciation and the emergence of human civilization; this period extends from 10,000 years BC to the present.</span></span>

sergeinik [125]3 years ago

6 0

your answer is Quaternary period

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What impulse occurs when an average force of 7.0 N is exerted on a cart for 2.5 s ?

makkiz [27]

Answer: $1.7\times 10$

Explanation:

Given

Force $F=7 N$

time interval $t=2.5 s$

Impulse is given by $=Force \times time\ interval\ for\ applied\ force$

$Impulse=7\times 2.5=17.5$

For two significant Figure

$Impulse=1.7\times 10$

7 0

3 years ago

Jet aircraft maintenance crews are required to wear protective earplugs. Members of a particular crew wear earplugs that reduce

Taya2010 [7]

Answer:

So the sound intensity level they would experience without the earplugs is 110.32dB.

Explanation:

Given data

Sound intensity by factor =215

Sound intensity level =87 dB

To find

Sound intensity level they would experience without the earplugs

Solution

First we need to find the new sound intensity level

$I_{n}=215(10^{\frac{87}{10} } )\\I_{n}=1.08*10^{11})$

The dB can be calculated as:

$dB=10log(I_{n})\\$

Substitute the given values

$dB=10log(1.08*10^{11})\\dB=110.32dB$

So the sound intensity level they would experience without the earplugs is 110.32dB.

7 0

3 years ago

Complete the following sentence.

notka56 [123]

Could it be "Scientific research"?

5 0

3 years ago

A Ray of light falling on rough surface follows the laws of reflection but no image of the object placed before it is C explain

stepladder [879]

Answer:

The light rays falling on a rough surface does follow the laws of reflection. The light rays are incident parallel on the rough surface but due to uneven surface the light rays are not reflected parallel rather they are reflected in different direction. Hence, no image is formed.

4 0

3 years ago

A weight suspended from a spring is seen to bob up and down over a distance of 20 cm triply each second. What is the period? Wha

Kisachek [45]

Answer:

1) Hence, the period is 0.33 s.

2) The amplitude is 10 cm.

Explanation:

1) The period is given by:

$T = \frac{1}{f}$

Where:

f: is the frequency = 3 bob up and down each second = 3 s⁻¹ = 3 Hz

$T = \frac{1}{f} = \frac{1}{3 Hz} = 0.33 s$

Hence, the period is 0.33 s.

2) The amplitude is the distance between the equilibrium position and the maximum position traveled by the spring. Since the spring is moving up and down over a distance of 20 cm, then the amplitude is:

$A = \frac{20 cm}{2} = 10 cm$

Therefore, the amplitude is 10 cm.

I hope it helps you!

5 0

3 years ago