Physics help-Inclined Plane Question

[Violagirl]

Question from ExamKrackers 1001 Questions in Physics, Problem 185:

If h is 5 m, m is 5 kg, theta is 30 degrees, and the mass starts from rest, how long does it take the mass to move the distance d?

A) 1 s

B) 1.4 s

C) 2 s

D) 3 s

I've been having a tough time with this problem. I know that you for the x-coordinate, that would you have to consider acceleration in a horizontal direction. So for forces in the x direction (horizontal), I get:

Fx = ma = mg cos theta

---> a = g cos theta

In the Y direction (vertical), I get Fy = 0, so Fy = N - mg sin theta so N - mg sin theta

I'm otherwise not sure how to determine "d." It has been a while since I've take physics so I'm not sure if I'm mapping out the free body diagram correctly or not. Any input would be appreciated. See the image for the picture of the diagram.

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[Hadi7183]

Since you didn't mention anything about friction, I assume it can be neglected. The component of acceleration parallel to the inclined surface is:

a=g*sin30=g/2=~5

Since h=5 and theta=30, then d=10. Use d=0.5*a*t^2 and find t. The answer should be sqrt(2)=1.4 s.

 

[popopopop]

^Yeah, it should be sin30 like he said.

so sin30 = 5/hypotenuse, hypotenuse = d = 10. Plug that into one of your kinematics equation d= v0(t) + 1/2at^2, solve for t.