Question

M is directionly proptional to r squared

when r=2, m=14

A)work out the value of m when r is 12

b) work out the value or r when m is 224

Answer 1

9514 1404 393

Answer:

A) 504

B) 8

Explanation:

The statement of proportionality can be written as the equation ...

m = kr²

Then we can find k from ...

k = m/r² = 14/2² = 7/2

That is, ...

m = (7/2)r²

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Using this relation, we can find m for r=12:

m = (7/2)·12² = 7·72

m = 504 . . . for r = 12

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And, we can use the same equation to solve for r when m=224.

224 = 7/2·r²

r² = 64

r = √64

r = 8 . . . for m = 224