A block sliding up a ramp, solve for acceleration

[acid234]

Homework Statement

A block is sent sliding up a 50 degree ramp at an initial speed of 9m/s. The coefficient of kinetic friction between the ramp and the block is 0.51. Find the acceleration of the block.

Homework Equations

Fk = (Fn)uk
F=ma

The Attempt at a Solution

umgsin50 = ma
ugsin50 = a
0.51(-9.8)sin50 = a
a = -3.829

Which is far from the right answer.

 

[206PiruBlood]

gravity! Think about if the block wasn't initially moving, would you know how to calculate its downward acceleration from gravity alone? The friction portion seems to be correct though.

 

[rl.bhat]

Hi acid234, welcome to PF.
On the inclined plane, the retardation is caused by two factors. 1) Component of the weight along the inclined plane and 2) the frictional force. Find them