A commonly used unit in everyday language to state weight is the pound (lb). There are actually several formal definitions of pound. One classification system defines a pound-mass (analogous to kg in SI units) and a pound-force (lbf) (analogous to a Newton); this is formally called English Engineering units but also commonly used in US Customary System units. The “pound” in the “pounds per square inch” of psi refers to pound-force. Hence, psi has units of force per area. Note that 1 lbf is defined as the gravitational force generated by 1 lb (mass) by multiplying it by the standard gravitational acceleration at the earth’s surface.Starting with just the two everyday conversion approximations every Canadian should know (1.00 kg ≈ 2.20 lb (mass) and 1.00 inch ≈ 2.54 cm), derive an approximation of 1.00 psi in Pa through unit conversions only (show each step).

Question
Asked Sep 28, 2019

A commonly used unit in everyday language to state weight is the pound (lb). There are actually several formal definitions of pound. One classification system defines a pound-mass (analogous to kg in SI units) and a pound-force (lbf) (analogous to a Newton); this is formally called English Engineering units but also commonly used in US Customary System units. The “pound” in the “pounds per square inch” of psi refers to pound-force. Hence, psi has units of force per area. Note that 1 lbf is defined as the gravitational force generated by 1 lb (mass) by multiplying it by the standard gravitational acceleration at the earth’s surface.

Starting with just the two everyday conversion approximations every Canadian should know (1.00 kg ≈ 2.20 lb (mass) and 1.00 inch ≈ 2.54 cm), derive an approximation of 1.00 psi in Pa through unit conversions only (show each step).

check_circleExpert Solution
Step 1

We have been given the following data:

1 kg 2.20 lb
1 in
2.54 cm
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1 kg 2.20 lb 1 in 2.54 cm

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Step 2

The expression for 1 psi can be written as,

1 lbf
1 psi=
1in
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1 lbf 1 psi= 1in

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Step 3

Convert the unit of 1 l...

1 lbf (1 lb)g
1
kg
|(1 lb) 2.20
1 lb
(9.806 m/s2)
1
kg (9.806 m/s2
2.20
=4.4482 N
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1 lbf (1 lb)g 1 kg |(1 lb) 2.20 1 lb (9.806 m/s2) 1 kg (9.806 m/s2 2.20 =4.4482 N

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