WARNING - Phys 101 Q Dropper Here

I am always challenging my kiddo to be better than me... Especially in math. We work hard to keep him engaged with his math homework and I always tell him the importance of excelling in this study. I even relate to him my story of performing poorly in math during my middle school years and getting hammered in my college math courses. NOT a fun experience for ole' dad.

Kiddo learned about Friction a few weeks ago and now wants to make a science fair project based on what he understands (5th Grade - so nothing crazy). His theory is that a rough item (sandpaper/cardboard) with have a higher Force of Friction than a smooth item (glass/tin foil). Kiddo will build a ramp that can be raised and lowered. An item of known mass and makeup (cardboard, sandpaper) will be set on top of the ramp and raised into the air until it breaks free. This would allow him to determine the Force of Friction. Can someone please check my equation and nomenclature?

Force of Friction (Newtons) = Coefficient of Friction * Normal Force

Coefficient of Friction = (length of base) * (height of the ramp at point the test object moves)

Normal Force = mass of test object * gravity

Used the following webpage for information:
https://sciencing.com/force-friction-knowing-coefficient-friction-8708335.html

Since this is a break-free type of experiment he will specifically be measuring the coefficient of static friction. The coefficient of kinetic friction happens once the object begins to move.

On your equations, just remember that since he will be using an incline plane, the normal force becomes:
Normal Force = mass of test object * gravity * cos(theta). Where theta is the angle of the incline plane.

Coefficient of static friction = Ff/Fn which just becomes sin(theta)/cos(theta). Ff is the static friction force and Fn is the normal force. Theta is the angle of the incline plane

Thank you! This is exactly the info I needed.

I completely agree a drag test would have been easier… Kiddo wants to build a ramp…. Ugh….

Thanks also for the video!

Alright, still working on figuring this out - cuz I am a huge dummy... But, my kiddo thinks it is hilarious so game on...

I am solving for Coefficient of Static Friction... Mass of our test object (wood with slick bottom) is 77 grams which broke free at 18.25 degrees (average of 4 tries - ramp is also slick). I first start by solving for Normal Force:

Normal Force = weight of object * gravity * cos(theta)
Normal Force = .077 kg * 9.81 m/s * 0.949699
Normal Force = .717 N (Am I figuring cos of 18.25 degrees incorrectly?)...

I assume we are converting grams to kilograms for Normal Force?

From what I am reading online the Coefficient of Static Friction is tan(Theta)... tan(18.25 degrees) = .32975

If true, then would Force of Friction = Coefficient of Static Friction * Normal Force???

Force of Friction = .32975 * .717 N
Force of Friction = .236 N

If anyone had a sec, could yall check my above math?

We also did wood blocks with tinfoil, rubberized foam, and cardboard on the bottom. These all slid down an inclined plane with a sheet metal covering (very slick).

Greek letter mu ()

Math looks good to me.

The reason you converted grams to kg is because a Newton = kg*(m/s^2).