Given: The pressure inside a tire (P) = 28.0 psi = 28.0 pound / inch²
And 1 pound = 4.45 newtons 1 inch² = 6.45 cm²
Calculation: We shall convert the given pressure in terms of Nm⁻²
Since,
1 pound / inch² = [1 pound× ( 4.45 N / 1 pound)] / [1 inch²× ( 6.45 cm² /1 inch²)]
or, = [1 pound× ( 4.45 N / 1 pound)] / [1 inch²× ( 6.45×10⁻⁴ m² /1 inch²)]
or, = 6.899 ×10³ Nm⁻²
The pressure inside a tire (P) = 28.0 psi
or, = 28.0 pound / inch²
or, = 28.0 × 6.899 ×10³ Nm⁻²
or, = 193.172 ×10³ Nm⁻²
or, = 1.93172 ×10⁵ Nm⁻²
Since the given measurements have three significant figures.
Hence, the required pressure in the correct significant figures ( three digits) will be 1.93 ×10⁵ N m⁻².
