Block pushed up frictionless incline

[mooneh]

a block is pushed up a frictionless 30 incline by an applied force
the force F=50 N and the mass = 3 kg
whats the magnitude of the resulting acceleration of the block ?


sol:
-Fcos30=ma
mg+Fsin30=ma

right answer for a=9.4

 

[Doc Al]

These problems will be easier to solve if:
(1) You draw yourself a free body diagram
(2) You use components parallel (and perpendicular) to the plane

In this case, apply Newton's 2nd law to force components parallel to the plane (since that's the only direction that the object can move).

(Extra hint: If you insist on using vertical and horizontal components, you will need to add the normal force into the mix.)

 

[rado5]

Right answer is a=11.77m/s$$^{}2$$
Because F-mgsin(30)=ma so 50-3*9.8*0.5=3a and a=11.77m/s$$^{}2$$