# physics

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A copper ball has a mass of 1kg.Calculate the radius of the ball,given that the density of copper is 8900kg m-3

• physics -

recall that the volume of a sphere (geometry of the ball) is given by
V = (4/3)πr^3
where
π = 3.14 (constant)
thus to get radius, we need to first get the volume from the given mass and density.
recall that density is just mass per volume, or
d = m/V
substituting,
8900 = 1/V
V = 0.0001124 m^3
substituting these to volume of sphere,
0.0001124 = (4/3)πr^3
0.0001124 = (4/3)*(3.14)*r^3
r^3 = 0.0001124 / 4.187
r = cuberoot(0.00002684)
r = 0.02994 or approx 0.03 m

hope this helps~ :)

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