Sliding down an incline?

Question

An object slides down an inclined plane of angle 20° and of incline length 3 m. If the initial speed of the object is 3 m/s directed down the incline, what is the speed at the bottom? Neglect friction.

Answer 1

because the velocity changes, we have an acceleration.
a=Fnet/m

draw a FBD and you'll see that Fweight(x) of the object is the net force.
a = Fweight(x) / m

break down Fweight(x)
Fweight(x) = sin(20)mg

a = sin(20)mg / m
the mass cancel out
a = sin(20)g
a = sin(20)9.8
a = 3.35m/s^2

Vf^2 = 2ad + Vo^2
Vf^2 = 2(3.35)(3) + 0^2
Vf^2 = 20.1
Vf = 4.48m/s

hope this helps

Answer 2

At the bottom the mass has a velocity of 5.4 m/sec. (directed down the incline of course).

Zeo... seems OK except about 5 lines from the bottom he carelessly "drops" your initial velocity; otherwise his answer would agree with mine.