A 3kg block starts at the top of a 30 degree incline and slides 2m down the incline in 1.5 seconds.(adsbygoogle = window.adsbygoogle || []).push({});

a) Find acceleration of the block.

b) Find the coefficient of kinetic friction between the blcok and the incline.

For a) x = vot + 1/2at^2 --> a = 1.778m/s^2

For b) *here's where i'm having some problems*

I tried doing it two different ways and i get two different answers.

Way 1:

Ff = uFn

Ff/Fn = u

mgsinx/mgcosx=u

tanx=u

u = .577

Way 2:

ΣF=ma

mgsinx - umgcosx = ma

gsinx - ugcosx =a

a-gsinx/-gcosx = u

(1.778m/s^2 - 5m/s^2)/-(10*cos30) = u

u = .372

which way is wrong?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Inclined plane question

**Physics Forums | Science Articles, Homework Help, Discussion**