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Hibbeler Statics 14E P1.4 — Conversion from English units to Metric Units

Convert: (a) 200 lb·ft to N·m, (b) 350 lb/ft3 to kN/m3, (c) 8 ft/h to mm/s. Express the result to three significant figures. Use an appropriate prefix.

Statics of Rigid Bodies 14th by RC Hibbeler, Problem 1-4

Solution:

Part A

200 lb⋅ft=(200 lb⋅ft)(4.4482 N1 lb)(0.3048 m1 ft)=271 N⋅m\begin{align*} 200\ \text{lb}\cdot \text{ft} & =\left( 200\ \text{lb}\cdot \text{ft} \right)\left( \frac{4.4482\ \text{N}}{1\ \text{lb}} \right)\left( \frac{0.3048\ \text{m}}{1\ \text{ft}} \right)\\ &=271\ \text{N}\cdot \text{m} \end{align*}

Part B

350 lb/ft3=(350 lb1 ft3)(1 ft0.3048 m)3(4.4482 N1 lb)(1 kN1000 N)=55.0 kN/m3\begin{align*} 350 \ \text{lb/ft}^3& = \left( \frac{350\ \text{lb}}{1\ \text{ft}^3} \right)\left( \frac{1\ \text{ft}}{0.3048\ \text{m}} \right)^3\left( \frac{4.4482\ \text{N}}{1\ \text{lb}} \right)\left( \frac{1\ \text{kN}}{1000\ \text{N}} \right)\\ & = 55.0\ \text{kN/m}^3 \end{align*}

Part C

8 ft/hr=(8 ft1 hr)(1 hr3600 s)(0.3048 m1 ft)(1000 mm1 m)=0.677 mm/s\begin{align*} 8 \ \text{ft/hr}& = \left( \frac{8\ \text{ft}}{1\ \text{hr}} \right)\left( \frac{1\ \text{hr}}{3600\ \text{s}} \right)\left( \frac{0.3048\ \text{m}}{1\ \text{ft}} \right)\left( \frac{1000 \ \text{mm}}{1 \ \text{m}} \right)\\ & = 0.677\ \text{mm/s} \end{align*}
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