# Typo?

#### theo tree

Heya,

Looking at an introduction to vectors.

In my textbook it gives the example question:

"A particle of mass 0.1kg is held at rest on a rough plane inclined at 20Â° to the horizontal by a friction force, F, acting up the plane. Find the magnitude of F and the normal reaction."

"F = 0.1g sin20Â° = 0.335 N"

Is this a typo, or is there something that I'm missing?

Thanks very much as ever

Theo

ps can anyone explain what's happening with the units here? How do you get from grams * degrees to Newtons?

#### theo tree

Right.

g is gravity, not grams.

Gotcha.

#### DarnItJimImAnEngineer

Might I add as an engineering instructor, if any of my students turned in a report with this in it, I would likely take points off and definitely reiterate the importance of clear communication. I would have accepted, "F = (0.1 kg) g sin 20Â°," or, better yet, "F = mg sinÎ˜ = (0.1 kg)(9.807 m/sÂ²)(sin 20Â°) = 0.335 N."

1 person

#### topsquark

Math Team
Right.

g is gravity, not grams.

Gotcha.
No. g is the acceleration due to gravity, not gravity (which is a force.)

-Dan

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