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earnstyle [38]
3 years ago
5

. A rock is dropped from a height of 4 m. How fast is it going when it hits the ground? The rock has a mass of 2 kg. (Hint: MEi

= MEf)
Physics
2 answers:
Lostsunrise [7]3 years ago
8 0

Answer:

8.85 m/s

Explanation:

Bas_tet [7]3 years ago
4 0

Hello!

When the rock is dropped, it only contains Gravitational Potential Energy, and when it hits the ground, it contains Kinetic Energy.

So:

PE = KE
\large\boxed{mgh = \frac{1}{2}mv^2}

We can rearrange to solve for velocity. Cancel out mass and solve.


gh = \frac{1}{2}v^2\\\\2gh = v^2\\\\v = \sqrt{2gh}

Plug in the givens:


v = \sqrt{2(9.8)(4)} = \boxed{8.85 \frac{m}{s}}

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Determine the angle between the directions of vector a = 3.00i 1.00j and vector b = 1.00i 3.00j .
Katena32 [7]

The angle between the two vectors is 126° 52' 11".

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vector B = 1.00i + 3.00j

The angle between the two vectors is calculated as follows;

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The dot product of vectors A and B is calculated as;

A.B = ( 3i + 1j ) . ( 1i +3j )

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The magnitude of vectors A and B is calculated as;

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The angle between in two vectors is calculated as;

Cos \theta = \frac{6}{\sqrt[]{10}\sqrt[]{10}  } \\\\Cos \theta = \frac{6}{\ 10 }\\\\Cos \theta = 0.6\\\\\theta = cos^-^1 (0.6)\\\\\theta = 126\\

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Learn more about vectors here:

brainly.com/question/25705666

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A person walks 1 mile every day for exercise, leaving her front porch at 9:00 am. and returning to her front porch at 9:25 am. W
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