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a_sh-v [17]
3 years ago
11

What is the approximate percentage of geologic time that humans have existed on earth since its origin?

Physics
1 answer:
Alekssandra [29.7K]3 years ago
5 0

Answer:about 200,000 years ago that humans existed on earth.

Explanation:Geologic time refers to the planet's changing geology. The earliest fossils of modern humans are from the middle Paleolithic about 200,000 years ago such as the omo remains from Ethiopia and the fossil of herto classified equally as homosapiens equally from Ethiopia.

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Mass is a fundamental quantity ​
Oliga [24]

Explanation:

okk hope you like then comment

5 0
3 years ago
it took 3.5 hours for a train to travel the distance between two cities at a velocity of 120 miles per hour. How many miles lie
Art [367]

Given:

Time: 3.5 hrs

Velocity: 120 miles/hr

Now Distance=  Speed × Time

Now Velocity and speed have the same magnitude. Velocity being a vector quantity has a definite direction. Whereas speed is a scalar quantity,it indicates only the magnitude an doesn't define any direction.

Hence Distance = Velocity x time

Distance = 3.5 × 120 = 420 miles

7 0
3 years ago
Hello,help me with this out please i need it hurry but please ensure your answer is correct..I attach here with my question.
lilavasa [31]

Answer:

.409 N

Explanation:

For this to balance, the moments around the fulcrum must sum to zero.

On the left you have   .21   ( is that down? I will assume it is)

      Counterclockwise moments :

        .21 * 40     +  1.0 * 20    

     Clockwise moments :

        .5 * 20     +     F * 45

these moments must equal each other

.21*40 + 1 *20   =  .5 * 20 + F * 45

   F = .409 N

7 0
1 year ago
Does the air exert a buoyant force on all objects in air or only on objects such as balloons that are very light for their size?
Citrus2011 [14]

Answer:

See explanation

Explanation:

Solution:-

Buoyancy is the force that causes objects to float. It is the force exerted on an object that is partly or wholly immersed in a fluid. Buoyancy is caused by the differences in pressure acting on opposite sides of an object immersed in a static fluid. It is also known as the buoyant force. Buoyancy is the phenomena due to Buoyant Force.

It is as an upward force exerted by a fluid that opposes the weight of an object immersed in a fluid. As we know, the pressure in a fluid column increases with depth. Thus, the pressure at the bottom of an object submerged in the fluid is greater than that at the top. The difference in this pressure results in a net upward force on the object which we define as buoyancy.

- The formula for buoyant force (Fb) is given:

                           Fb = ρ*g*V

- The force acts on all objects. However, it depends on the fluid density and amount of volume displaced.

- The Buoyant force exerted by air with density = 1.225 kg/m^3 on an object with volume (V) is:

                          Fb = ρ*g*V = 1.225*9.81*V = 12.02*V

- For the similar object with mass (m), the downward weight would be:

                           W = m*g

- For the object to float the buoyant force (Fb) must be greater than weight of the object:

                          Fb > W

                          12.02*V > m*9.81

                          V / m > 0.816

- The ratio of V / m must be at-least = 0.816.

- Assuming the object is fully immersed in air, then the volume displaced V = ρ_material*V

                         ρ_material < 1 / 0.816

                        ρ_material < 1.225 or ( ρ_air )

- So the for an object to float in air its material density must always be less than that of air. That why in balloons lighter gas is used which have density less than that of air like Helium.          

4 0
3 years ago
What would be the projectile's initial speed?
zalisa [80]

Math is the process of using the given information, along with
all the general stuff that you know, to find the missing information. 
With no given information, we have no way to even guess at
an answer.

8 0
3 years ago
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