Question

6.
The mass of a disc cut out of an iron
plate is proportional to the square of the radius of the disc. If a disc with a radius equal to 15 cm has a mass of 1.80kg,what will the radius of adisc with a mass of 0.20 kg?​

Answer 1

Answer:

1.25

Step-by-step explanation:

6.

6.The mass of a disc cut out of an iron

6.The mass of a disc cut out of an ironplate is proportional to the square of the radius of the disc. If a disc with a radius equal to 15 cm has a mass of 1.80kg,what will the radius of adisc with a mass of 0.20 kg?

Answer 2

Answer:

Radius of the disc with mass of 0.20 kg is 5 cm.

Step-by-step explanation:

The mass of a disc cut out from an iron plate is proportional to the square of the radius of the disc.

m ∝ r

Or m = kr

where k = proportionality constant.

If radius of two discs are r and r' respectively.

Similarly, masses of the different discs are m and m'

For disc 1,

m = kr² -----(1)

For disc 2,

m' = k(r')² -------(2)

Equation (1) ÷ Equation (2)

$\frac{m}{m'}=(\frac{r}{r'})^{2}$

If r = 15 cm, m = 1.80 kg and m' = 0.20 kg then

$\frac{1.80}{0.20}=(\frac{15}{r'})^{2}$

$9=\frac{225}{(r')^{2} }$

r' = $\sqrt{\frac{225}{9} }$

r' = 5 cm

Therefore, radius of the disc with mass of 0.20 kg is 5 cm.

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