Frictionless inclined plane physics homework

[IB]

A 2.0 kg mass slides down a frictionless inclined plane that makes an angle of 30 degrees with the horizontal. The sass starts from rest. What is its speed after it has slid a distance of 3.0 m along the incline?

I got:

F = (sin30)(9.8)
F = 4.9 N

W = Fd
W = (4.9) (3) = 14.7 J

W = E_kin
14.7 J = 1/2 mv^2
v = 1.21 m/s

Is my method correct? I'm very unsure how to do this one. Thanks.

 

[lightgrav]

your Work-Energy method is excellent ...
but a few chapters ago, F = M g sin (theta)
. . . if you had USED units [kg N/kg] you would have caught your error.

 

[IB]

F = M g sin (theta) ?

I'm not sure what you mean.

 

[daniel_i_l]

you forgot the mass when you calculated the force.