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aleksandr82 [10.1K]
3 years ago
13

The word “cumulative” means that something builds on itself. Which example best shows how scientific knowledge is cumulative? A.

Watson and Crick worked together to come up with the model of DNA. B. Kepler based his laws of planetary motions off of Newton’s law of gravity. C. Hardy and Weinberg independently came up with a population equation. D. Darwin and his grandfather both worked on the ideas of survivability.
Physics
1 answer:
ioda3 years ago
4 0

Answer:

B

Explanation:

Kepler embodied cummulative knowledge(succession).

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An investigation involves determining which metal is better for making pots that will cook food faster. Which is the best hypoth
irina [24]
Because the specific metals aren’t mentioned in this inquiry. The educational guesses that we can propose is that:
<span><span>1.    </span>The hypothetical inquiry: There are existing metals for making pots that will cook food much faster.</span>

<span><span>2.    </span>The one-tailed alternative hypothesis: There are other metals for making pots that will cook food much faster than the other metals.</span> <span><span>
3.    </span>The one-tailed null hypothesis: All metals that are used in making pots will cook food at an equal rate.</span>



8 0
3 years ago
A rocket is moving at 1/4 the speed of light relative to Earth. At the center of this rocket a light suddenly flashes. To an obs
Sedaia [141]

Answer:

B. the light will reach the front of the rocket at the same instant that it reaches the back of the rocket.

Explanation:

To an observer at rest in the rocket who can't see either sides of the rocket, the speed of the light is constant which means the distance to the front or the back is same and would appear to reach the rocket at the same time.

Although from the point of view of the person on the earth, the front of the rocket is travelling in opposite direction of the light while the back of the rocket is moving closer to the light. This means that the distance travelled by the light going forward will be longer going backwards. And since the speed of light is constant in both directions, the light will reach the back of the rocket before it reaches the front  for the observer on the earth.

5 0
3 years ago
Read 2 more answers
A rock is thrown upward from the top of a 30 m building with a velocity of 5 m/s. Determine its velocity (a) When it falls back
castortr0y [4]

Answer:

a) 5 m/s downwards

b) 17.86 m/s

c) 24.82 m/s

d) 0.228

Explanation:

We can set the frame of reference with the origin on the top of the building and the X axis pointing down.

The rock will be subject to the acceleration of gravity. We can use the equation for position under constant acceleration and speed under constant acceleration:

X(t) = X0 + V0 * t + 1/2 * a * t^2

V(t) = V0 + a * t

In this case

X0 = 0

V0 = -5 m/s

a = 9.81 m/s^2

To know the speed it will have when it falls back past the original point we need to know when it will do it. When it does X will be 0.

0 = -5 * t + 1/2 * 9.81 * t^2

0 = t * (-5 + 4.9 * t)

One of the solutions is t = 0, but this is when the rock was thrown.

0 = -5 + 4.69 * t

4.9 * t = 5

t = 5 / 4.9

t = 1.02 s

Replacing this in the speed equation:

V(1.02) = -5 + 9.81 * 1.02 = 5 m/s (this is speed downwards because the X axis points down)

When the rock is at 15 m above the street it is 15 m under the top of the building.

15 = -5 * t + 1/2 * 9.81 * t^2

4.9 * t^s -5 * t - 15 = 0

Solving electronically:

t = 2.33 s

At that time the speed will be:

V(2.33) = -5 + 9.81 * 2.33 = 17.86 m/s

When the rock is about to reach the ground it is at 30 m under the top of the building:

30 = -5 * t + 1/2 * 9.81 * t^2

4.9 * t^s -5 * t - 30 = 0

Solving electronically:

t = 3.04 s

At this time it has a speed of:

V(3.04) = -5 + 9.81 * 3.04 = 24.82 m/s

---------------------

Power is work done per unit of time.

The work in this case is:

L = Ff * d

With Ff being the friction force, this is related to weight

Ff = μ * m * g

μ: is the coefficient of friction

L = μ * m * g * d

P = L/Δt

P = (μ * m * g * d)/Δt

Rearranging:

μ = (P * Δt) / (m * g * d)

1 horsepower is 746 W

20 minutes is 1200 s

μ = (746 * 1200) / (100 * 9.81 * 4000) = 0.228

8 0
3 years ago
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tatuchka [14]
V(voltage) = I(current)R(resistance)
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Force=A×M
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