Question

A poundal is the force required to accelerate a mass of 1 lbm at a rate of 1 ft/s2, and a slug is the mass of an object that will accelerate at a rate of 1 ft/s2 when subjected to a force of 1 lbf.
(
a. Calculate the mass is slugs and the weight in poundals of a 175 lbm man (i) on earth and (ii) on the moon, where the acceleration of gravity is one-sixth of its value on earth.
(
b. A force of 355 poundals is exerted on a 25.0-slug object. At what rate (m/s2) does the object accelerate?

Answer 1

a. Calculate the mass is slugs and the weight in poundals of a 175 lbm man (i) on earth and (ii) on the moon, where the acceleration of gravity is one-sixth of its value on earth.

The weight is the attraction force exerted by the earth (or moon) on the body

This force is calculated by the second Law of Newton: F = m*a = m*g = weight.

i) In the Earth:

m = 175 lbm
g = 32.17 ft/s^2

=> Weight = 175 lbm * 32.17 ft/s^2 = 5,629.75 poundal

ii) g = 1/6 * 32.17 ft/s^2 = 5.36 ft/s^2

=> Weight = 175 lbm * 5.36 ft/s^2 = 938 poundal



b. A force of 355 poundals is exerted on a 25.0-slug object. At what rate (m/s2) does the object accelerate?

Second Law of Newton: F = m*a => a = F/m

a = 355 poundal / 25.0 slug = 14.2 ft/s^2

Conversion to m/s^2:

14.2 ft/s^2 * [0.3048 m/ft] =  4.33 m/s^2