Question

M is directly proportional to r squared

When r= 2, M= 14
a) Work out the value of M when r= 12.
b) Work out the value of r when M = 224.

Answer 1

Explanation:

`m \alpha r ^(2)`

`m = kr ^(2)`

`14 = k * 2 ^(2)`

`14 = 4k`

`(14)/(4) = k`

`3.5 = k`

a.

`m = kr ^(2)`

`m = 3.5 * 12^(2)`

`m = 504`

b.

`m = kr ^(2)`

`224 = 3.5r ^(2)`

`(224)/(3.5) = r ^(2)`

`64 = r ^(2)`

`√(64) = \sqrt {r}^(2)`

`8 = r`