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Different Kinds of Friction
Dry friction is just like it sounds – if you’ve ever tried to shove a heavy box across the pavement, you know that it’s harder to get it started than keep it going. That’s because when you first start to shove the box, you’ve got to overcome the (stronger) static friction, but once you’re moving you are dealing with only with the (weaker) kinetic friction. Sometimes kinetic friction is called ‘sliding’ or ‘dynamic’ friction.
Engineers and scientists reduce friction by adding lubrication, like oil. Your car engine uses oil to slick up the metal-to-metal surfaces and keep the pistons moving smoothly.
One of the troubles with liquids is that they tend to heat up quickly (there’s still friction between the liquid and the solid surface!), so you have to devise a system to cool the liquid. You can also use gas as a lubrication. Hovercraft ride on a cushion of air, using air as the ‘lubrication’ between the skirt and the ground.
Fluid friction is when you have two fluids flowing up against each other, like a stream of water and a stream of oil together. Skin friction happens when an airplane flies through the air – the air rushing by the airplane body heats up the outside of the aircraft.
Contrary to earlier explanations found in textbooks, we now know that kinetic friction happens not because of surface roughness, but rather because of the chemical bonding that happens between the two surfaces.
Click here to get started with the experiments!
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Yes, it sure does! The more the weight (or mass), the higher the force of friction. Think of how hard it is to slide a 100 pound box across the floor versus a 10 pound box. Just getting it started (overcoming static friction) takes more force!
Oops- I meant SHOE experiment under friction…
We are doing the show experiment and are wondering if the weight of the show has an effect on friction. Should that be something we add to our data?
Well, after reading over this page, what did you figure out?
What is friction
Are there only 5 kinds of mechanic friction (i.e. Static, Kinetic, Dry, Fluid, & Skin )?
Just ‘friction’. Sometimes ‘dry friction’. 🙂
We were wondering what the friction between a liquid and solid is called (you mentioned the two solids= dry friction, and the two liquids= fluid friction). Also, is there friction between gasses and what is it called? thanks
Hmmm… we just checked the link on this page and it seems to be working correctly:
https://www.sciencelearningspace2.com/category/unit-1-mechanics/lesson-3-friction/friction-video/?redirect_to=/category/unit-1-mechanics/lesson-3-friction/friction-video/
Try clicking on the link above, waiting for a few minutes and then hitting ‘play’… does that help? Sometimes if the streaming-rate of the video is slower than the play-rate, you can hit a bump like this. Let me know if you still need help – use our Contact Us page so we can get right back to you.
Thanks,
Aurora
We were listening to our first telecast on friction and all of a sudden it stops in the middle of a word – when you’re rubbing your hands together.
I’m assuming there’s more ?…………….
Bullets are hot because the friction between the air and the surface of the bullet heat it up… just like when you vigorously rub your hands together, they get warm. Same idea. 🙂
is this why bullets are hot when they hit someone?
Hmmm… looks like it works in IE but not Firefox. Let me see if our team can get that fixed…
it seems that the search bar on your site is not working. Is anyone else having a problem? Just wondering if it is my computer.