- #1
aeroengphys
- 21
- 0
A 3kg block starts at the top of a 30 degree incline and slides 2m down the incline in 1.5 seconds.
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?
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?