Physics HW problem: Block of mass 270 kg slides on a frictionless plane inclined at 35 degrees with?

Question

the horizontal under the influence of a restraining force of 1064 N acting parallel to the include and up the incline. Down the plane is positive and up is negative direction. Acceleration of gravity is 9.8 m/s2.

What is the magnitude of accelaration of the block (answer in m/s)?

The resulting motion is: a) up the plane, acceleration is negative
b) down the plane, acceleration is positive
c) undetermined

Answer 1

Acceleration up the plane caused by the restraining force:
a_up = F/m = -1064/270 = -3.94 m/s^2

Acceleration down the plane caused by gravity:
a_down = G sin(35) = 5.62 m/s^2

=> net acceleration = 5.62-3.94 = 1.68 m/s^2 down the plane