piper210_355

ok i think that i found an equation that could help me with this: F(f)=uF(normal) But how would i find the normal force? in another problem it was the mass times gravity, but in that problem the object was on the ground. Would it be different since it is vertical? or does that only apply to the vector components F=F(x)+F(y)+F(z) such that F(y) isn't 0 now, but instead it is the kinetic friction maybe? i don't know. I think i might be getting closer to getting it but i'm not completely sure.

ok i looked over my physics book and i think i solved it i used this equation to get the static friction: u=F(s),max/(mass)(gravity) i did it for the 2kg box when it was being pulled first. U(s)=18/(2)(9.81) I got .92. The next part is what i don't know if you can do or not i used the same equation for when both boxes are being pushed, and i put .92 as the static friction for that (although i'm not sure if i can do that). .92= 56/(2x)(9.81) I got 3.10kg

yes that's the way it's written in my book.

Well i know that gravity is pushing down on the box and the board is pushing up on it. I'll take a guess and say that when the box starts to move the force of gravity is greater then the force of the board, causing the box to move down.

I know that the initial velocity is 0. I know that in this case the normal force would be found by dividing the force of friction by the coeffiecent of friction. Is that what you mean? Are the static and kinetic friction the force of friction? And if so how do i find the coeffiecent of friction? *I apologieze if this is way off, but I'm just gathering facts from my book and stuff i'm finding on the internet and trying to make sense of it all.

I know that F(friction)=mF(normal) but i don't know how to find these I know that normal force is the weight of the object in this case, since it is parallel to the ground.

I think i know how to go about finding the acceleration now, but how do I find what the angle is? I just need to know what equations to use and i think i'll be good from there. don't i need to know what the angle is to find the normal force?

That's all the info that is given in the problem there is a picture, but it only shows that there is a 20 degree angle, if that's what your talking about. I added that to the post though

I know that acceleration equals final velocity minus initial velocity over time. other than that i don't know what to do. I have no idea how to find theta or what to do with the friction. Like i said my teacher hasn't taught me anything. I just need an explaination of how to do it.

Like i sayed in my other posts this is probably easy but my teacher doesn't teach us anything so i don't have a clue how to do this. Can someone please explain how to do it? A window washer pushes a sponge up a vertical window at a constant speed by applying a force. The sponge has a mass of .800 kg, and the coefficient of kinetic friction between the sponge and window is u_k=0.253. Determine the magnitude of the applied force, and the magnitude of the normal force exerted by the window on the sponge. *There is a 20 degree angle

Can someone please help me. My teacher hasn't taught us anything, yet she expects us to be able to do this. A 2.00 kg box is at rest on a horizontal floor. A horizontal force of 18.0 N is required to keep the 2.00 kg box moving across the floor at constant speed. A box of unknown mass is stacked on top of the 2.00 kg box. A horizontal force of 56.0 N applied to the 2.00 kg box is required to keep both boxes moving across the floor at constant speed. What is the mass of unknown box?

Okay so this is probably a really easy problem, but my teacher literally doesn't teach us any thing, so can someone please help me. The coefficient of static friction between a 2.5kg box and a wooden board is .45 and the coefficient of kinetic friction between the box and the board is .28. The box is placed on the board, which is slowly lifted at one end until the box starts to slide down the board, at which point the angle theta of the board is held constant. Determine the angle theta of the board and the acceleration of the box as it slides down the board.