- #1
chwala
Gold Member
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- Homework Statement
- A block of wood of mass ##4## kg is released from rest on a plane inclined at ##30^0## to the horizontal. Assuming that the surface is modelled as smooth (no friction), calculate the acceleration of the block, and its speed after it has moved ##3## m.
- Relevant Equations
- Mechanics
Pretty straight forward, ...reason of posting is to check why i am having a negative value for ##a##.
From my study, i know that
##R(||)## to plane
##F - 40 \cos \dfrac{π}{3} = 4a##
##a = -5 m/s^2##
or can i as well have the equation ( friction and tension are at equilibrium) as,
##40 \cos \dfrac{π}{3} - F = 4a##
For second part,
##v^2 =u^2 +2as##
##v^2= 2×5×3##
...
##v = 5.48 m/s## to two decimal places.
From my study, i know that
##R(||)## to plane
##F - 40 \cos \dfrac{π}{3} = 4a##
##a = -5 m/s^2##
or can i as well have the equation ( friction and tension are at equilibrium) as,
##40 \cos \dfrac{π}{3} - F = 4a##
For second part,
##v^2 =u^2 +2as##
##v^2= 2×5×3##
...
##v = 5.48 m/s## to two decimal places.
