Source: Extra Practice

The radius of a sphere is measured as (2.0±0.1) cm(2.0 \pm 0.1) \text{ cm}. What is the percentage error in the volume of the sphere? (Volume V=43πr3V = \frac{4}{3}\pi r^3)

Options

Option A

5%5\%

Option B

10%10\%

Option C is correct

15%15\%

Option D

20%20\%

Explanation

The formula for the volume of a sphere is V=43πr3V = \frac{4}{3}\pi r^3. The constants 43\frac{4}{3} and π\pi are exact and do not contribute to the error. For a quantity X=rpX = r^p, the fractional error is ΔXX=pΔrr\frac{\Delta X}{X} = p\frac{\Delta r}{r}. In this case, for V=r3V = r^3, the fractional error in volume is ΔVV=3Δrr\frac{\Delta V}{V} = 3\frac{\Delta r}{r}. Given radius r=2.0 cmr = 2.0 \text{ cm} and absolute error Δr=0.1 cm \Delta r = 0.1 \text{ cm}. Fractional error in radius Δrr=0.12.0=0.05\frac{\Delta r}{r} = \frac{0.1}{2.0} = 0.05. Now, calculate the fractional error in volume: ΔVV=3×0.05=0.15\frac{\Delta V}{V} = 3 \times 0.05 = 0.15. To convert this to percentage error, multiply by 100%100\%: Percentage error in volume =0.15×100%=15%= 0.15 \times 100\% = 15\% .