BR Physics Question: Friction while skiing

[salsasunrise123]

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Hi, I am kinda confused about skiing passage in the 25-q test. The question about side-stepping up hill is confusing me. I don't understand why friction is a horizontal force pointing in same direction as motion. Can someone please explain this to me. I am especially confused about how it is a horizontal force. Thanks.

 

[Cmdr_Shepard]

Same idea as car tires.

When you step, you push the skis towards the back/bottom with your feet, and the friction between the snow and the skis oppose this motion (friction always points in the direction opposing motion). So while your skis relative to the snow can move back, your frictional force points forward (in the same direction as your body).

It's kinda hard to explain without a diagram and while typing on my phone, but hopefully you get the idea.

 

[salsasunrise123]

so is it safe to say that when you have an object that starts from rest and then moves on surface where static friction is present, that the friction is in direction of movement and horizontal? I have trouble visualizing a situation where it would be in vertical direction. Thanks. You've been tons of help!

 

[Oso]

so is it safe to say that when you have an object that starts from rest and then moves on surface where static friction is present, that the friction is in direction of movement and horizontal? I have trouble visualizing a situation where it would be in vertical direction. Thanks. You've been tons of help!

Friction is in the direction that opposes motion. If you're pushing a box across a flat surface, the box is being pushed forward, so friction points backward. When you walk, you push your foot backwards (behind you), so friction points in the direction in front of you (the direction that you're walking in). Both of these are examples of friction along the horizontal axis.

An example of vertical friction would be sliding something across a vertical surface surface (like a wall).