Converting Slugs to Newtons: A Quick Guide for Solving Physics Problems

[Mitchell]

I am working a Physics problem where the mass is given as 20 slugs. To obtain Newtons can I just multiply 20 slugs x (14.59 kg/1 slug) x 9.80 m/s^2 = 2859.64N?

 

[Gokul43201]

Yes, that's right !

Make sure it is the mass that is described as 20 slugs, because slug is also a unit of force itself !

 

[Doc Al]

Careful. Since a slug is a unit of mass, not force, you can't "convert" slugs to Newtons. But if you are trying to find the weight of a 20 slug mass, then you are fine. (Your conversion of slugs to kilograms is correct.)

 

[Mitchell]

So is the mass of a slug 1lb.? And if so, to obtain (mass x gravity) in the U.S. Customary System would it just be 1 x 32 ft/sec^2 to obtain its weight?

 

[Doc Al]

So is the mass of a slug 1lb.? And if so, to obtain (mass x gravity) in the U.S. Customary System would it just be 1 x 32 ft/sec^2 to obtain its weight?

In the "British Engineering" System, the unit of mass is the slug and the unit of force is the pound. (Yes, sometimes the pound is also used as a unit of mass--but in my opinion, this is a bad idea in a physics course. 1 pound mass = 0.45359237 kg) The weight of a 1 slug mass is given by W=mg = (1 slug) (32 ft/s^2) = 32 pounds (approximately) as you noted.

 

[Mitchell]

Thank you. It's very confusing but your last explanation worked and resulted in a correct answer. I hate it when I get the Free body diagrams right, setting up the 2 equations with two unknowns right, and missing the correct answer due to conversion errors. Again...thank you for your help.