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a child wants to pump up a bicycle tire so that its pressure is 1.2 × 10⁵ pa above that of atmospheric pressure. if the child uses a pump with a circular piston 0.035 m in diameter, what force must the child exert? the area of a circle is (π/4)d²
76 n
240 n
89 n
54 n
120 n

Explanation:

Step1: Calculate piston area

Area formula: $A = \frac{\pi D^2}{4}$. $D=0.035\,\text{m}$, so $A = \frac{\pi (0.035)^2}{4} \approx 9.621 \times 10^{-4}\,\text{m}^2$.

Step2: Compute force using $F=P\times A$

$P=1.2\times10^5\,\text{Pa}$, so $F = 1.2\times10^5 \times 9.621\times10^{-4} \approx 115.45\,\text{N}$ (≈120N).

Answer:

120 N