# Friction acting on block [closed]

The frictional force acting on the block if it does not slide relative to the wedge which moves with an acceleration a towards right is

Friction $f$ and the component of pseudo force ($ma$) act up the incline and down the incline $mg\sin\theta$ Is acting, which gives $f+ma\cos\theta=mg\sin\theta$ which gives $f$ as $m(g\sin\theta-a\cos\theta)$, but the answer is given as $m(a\cos\theta-g\sin\theta)$.

Please tell me what am I doing wrong.

## closed as off-topic by garyp, ZeroTheHero, Bill N, Kyle Kanos, Jon CusterSep 4 '17 at 16:13

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$f$ does not act up the incline but down the incline. The sign is opposite and then the whole thing fits.