Once again, need help with mechanics, this one I think I did right, but my friend did it somehow different, and I was wondering who of us 2 is right(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

A block slides down an inclined plane of slope angle (alpha) with constant velocity. It is then projected up the same plane with an initial speed V0. How far up the incline will it move before coming to rest?Will it slide down again?

2. Relevant equations

F=ma

3. The attempt at a solution

What I did:

Y coordinate

-mg * Cos(alpha)+N=ma(y)=0

X coordinate

ma(x)=-F(friction)+mgSin(alpha)

F(fric)=mgsin(alpha)

WHEN BLOCK SLIDES UP

mgsin(alpha)+F(gravity)=ma(x)

2mgsin(alpha)=ma(x)

a(x)=2gSin(alpha)

S=-V^2/(4gsin(alpha))

What my friend did:

F(fric)=N * μ = mg * cos(α) * μ

F(fric)=mg* sin(α)=mg* cos(α)* μ

μ = tg(α)

S=V0t -0.5at^2

a=μ * mg * sin(α)

t=V0/a

S=V0^2/a -V0^2/(2a),

where a= sin^2(α)/cos(α) * mg

Oh and I don't really know whether it will slide down or not, I hope you guys can help me!

Thanks in advance.

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# Homework Help: Need help with mechanics

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