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3 years ago

6

I have no idea so i'm screwed please help me

1 answer:

podryga [215]3 years ago

8 0

Answer:

Let N0 be the initial atoms of Be11

N0 / 2^1 = N0 / 2 Number of Be11 after 1 half-life

N0 / 2^2 = N0/ 4 Number of Be11 after 2 half-lives

30/13.81 = 2.17 half lives

N0 / 2^2.17 = N0 / 4.51 = .222 N0 or 22.2 % of atoms remain

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mafiozo [28]

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3 years ago

To test the quality of a tennis ball, you drop it onto the floor from a height of 4.00 m. It rebounds to a height of 2.00 m. If

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Answer:

Part a)

$a = 1260.3 m/s^2$

Part b)

Direction = upwards

Explanation:

When ball is dropped from height h = 4.0 m

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Part a)

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Answer:

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Explanation:

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$\Sigma F_{x} = P+T-\mu_{k}\cdot N = 0$ (Ec. 1)

$\Sigma F_{y} = N - W = 0$ (Ec. 2)

Where:

$P$ - Pushing force, measured in newtons.

$T$ - Tension, measured in newtons.

$\mu_{k}$ - Coefficient of kinetic friction, dimensionless.

$N$ - Normal force, measured in newtons.

$W$ - Weight of the crate, measured in newtons.

The system of equations is now reduced by algebraic means:

$P+T -\mu_{k}\cdot W = 0$

And we finally clear the coefficient of kinetic friction and apply the definition of weight:

$\mu_{k} =\frac{P+T}{m\cdot g}$

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