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3 years ago

I need help. +brainliest. 25 pts+

Mathematics

1 answer:

Inga [223]3 years ago

4 0

Answer:

i cant help with the first one but the others i think i can

- plastic (insulator) -stainless steel (conductor) -silver (conductor) -wood (insulator)

Also radiation could effect the system but changing the conductivity of some of the materials also change change the way the materials accept heat.

Sorry about the first one :)

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c 8,800 yards

Step-by-step explanation:

1 mile = 1760 yards

5 miles = 5 * 1760 yards = 8,800 yards

Answer: c 8,800 yards

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What is the sum of 8a<br> 7+ 5b2 – 2a2 and 7b2 + 66_<br> 20a + 3?

barxatty [35]

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Step-by-step explanation:

7+5b²-2a²+7b²+66-20a-3

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5 0

3 years ago

a boy is standing on a pole of height 14.7m throws a stone upwards. it moves in a vertical line slightly away from the pole and

fomenos

Answer:

The time taken for the upward motion is 1 second. The same time is taken for the downward motion

It reaches a maximum height of 4.9 meters.

Step-by-step explanation:

The equation of motion is:

$x(t) = -4.9t^{2} + 9.8t$

Since the term which multiplies t squared is negative, the graph is concave down, that is, x increases until the vertex, where it reaches it's maximum height, then it decreases.

Vertex of a quadratic equation:

Quadratic equation in the format $x(t) = at^{2} + bt + c$

The vertex is the point $(t_{v}, x(t_{v}))$ , in which

$t_{v} = -\frac{b}{2a}$

In this question:

$x(t) = -4.9t^{2} + 9.8t$

So $a = -4.9, b = 9.8$

Vertex:

$t_{v} = -\frac{9.8}{2*(-4.9)} = 1$

The time taken for the upward motion is 1 second.

$x(t_{v}) = x(1) = 9.8*1 - 4.9*(1)^{2} = 4.9$

It reaches a maximum height of 4.9 meters.

Downward motion:

From the vertex to the ground.

The ground is t when x = 0. So

$-4.9t^{2} + 9.8t = 0$

$4.9t^{2} - 9.8t = 0$

$4.9t(t - 2) = 0$

$4.9t = 0$

$t = 0$

$t - 2 = 0$

$t = 2$

It reaches the ground when t = 2 seconds.

The downward motion started at the vertex, when t = 1.

So the duration of the downward motion is 2 - 1 = 1 second.

5 0

3 years ago