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3 years ago

How long ago did homo sapiens first appeared in the fossil record? Identify the era in which this occurred.

Physics

2 answers:

zvonat [6]3 years ago

6 0

Answer:

Explanation:

First fossil record of homo sapiens is dating back to 300,000 years ago which is found at the site in Morocco. During the 1960's mining began at the limestone hill in Morocco and during mining human skulls, bones and stone artifacts were found. Initial study of artifacts revealed that these are around 40,000 years ago, however, efforts were made again in 2004 and site is still under excavation. According to me this period should fall under Paleozoic Era.

Hope this will help.

AVprozaik [17]3 years ago

3 0

First discovery - Herto, Ethopia. 160,000 years ago - 40,000 years earlier than the previous oldest remains homo sapiens.

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A vehicle approaches a set of traffic lights with a speed of 15m/s. When 50m from the lights the driver brakes and comes to a re

sattari [20]

Answer:

–2.25 m/s²

Explanation:

From the question given above, the following data were obtained:

Initial velocity (u) = 15 m/s

Distance travelled (s) = 50 m

Final velocity (v) = 0 m/s

Deceleration (a) =?

v² = u² + 2as

0² = 15² + (2 × a × 50)

0 = 225 + 100a

Collect like terms

0 – 225 = 100a

– 225 = 100a

Divide both side by 100

a = –225/100

a = –2.25 m/s²

Thus, the deceleration of the vehicle is –2.25 m/s²

3 0

3 years ago

Consider a current carrying a wire coming out of your computer screen towards you. Which statement below correctly describes the

Ugo [173]

Answer:

1. The magnetic field encircles the wire in a counterclockwise direction

Explanation:

When we have a current carrying wire perpendicular to the screen in which the current flows out of the screen then by the Maxwell's right-hand thumb rule we place the thumb of our right hand in the direction of the current and curl the remaining fingers around the wire, these curled fingers denote the direction of the magnetic field which is in the counter-clock wise direction.

Ever current carrying conductor produces a magnetic field around it.

5 0

4 years ago

Olivia is on a swing at the playground. if the swing is moving from W to Z, at which point is her kinetic energy increasing and

s2008m [1.1K]

Answer:

from W-Z.. i think on a swing you get your most potential energy at W and Z is where you go up so Z would be where the kinetic energy increased and W is where potential energy decrease

Explanation:

hope this helps

4 0

3 years ago

The electric field on the surface of an irregularly shaped conductor varies from 74.0 kN/C to 14.0 kN/C.

mrs_skeptik [129]

Answer:

(a). The local surface charge density at the point on the surface where the radius of curvature of the surface is greatest is 123.9 nC/m².

(b). The local surface charge density at the point on the surface where the radius of curvature of the surface is greatest is 654.9 nC/m².

Explanation:

Given that,

Electric field $E_{1}=74.0\ kN/C$

Electric field $E_{2}=14.0\ kN/C$

When the radius of curvature is greatest, the electric field at the surface will be smaller.

Where the radius of curvature is greatest

(a). We need to calculate the local surface charge density at the point on the surface

Using formula of charge density

$\sigma=\epsilon_{0}E_{2}$

Put the value into the formula

$\sigma=8.85\times10^{-12}\times14\times10^{3}$

$\sigma=1.239\times10^{-7}\ C/m^2$

$\sigma=123.9\times10^{-9}\ C/m^2$

$\sigma=123.9\ nC/m^2$

The local surface charge density at the point on the surface where the radius of curvature of the surface is greatest is 123.9 nC/m².

(b). We need to calculate the local surface charge density at the point on the surface where the radius of curvature of the surface is smallest

Using formula of charge density

$\sigma=\epsilon_{0}E_{1}$

Put the value into the formula

$\sigma=8.85\times10^{-12}\times74\times10^{3}$

$\sigma=6.549\times10^{-7}\ C/m^2$

$\sigma=654.9\times10^{-9}\ C/m^2$

$\sigma=654.9\ nC/m^2$

The local surface charge density at the point on the surface where the radius of curvature of the surface is greatest is 654.9 nC/m².

Hence, (a). The local surface charge density at the point on the surface where the radius of curvature of the surface is greatest is 123.9 nC/m².

(b). The local surface charge density at the point on the surface where the radius of curvature of the surface is greatest is 654.9 nC/m².

7 0

3 years ago

In a two-source circuit, one source acting alone produces 10 ma through a given branch. the other source acting alone produces 8

pashok25 [27]

Refer to the figure below.
R = resistance.

Case 1:
The voltage source is V₁ and the current is 10 mA. Therefore
V₁ = (10 mA)R

Case 2:
The voltage source is V₂ and the current is 8 mA. Therefore
V₂ = (8 mA)R

Case 3:
The voltage across the resistance is V₁ - V₂. Therefore the current I is given by
V₁ - V₂ = IR
10R - 8R = (I mA)R
2 = I
The current is 2 mA.

Answer: 2 mA

6 0

3 years ago