Aball starting from rest at the top of an inclined plane accelerates at 2 m/s2 and reaches the bottom of the plane in 3 seconds. what is the length of the plane

What you must do in this case is write the kinematic equations to find the length of the plane.
 We have then:
 a = 2 m / s ^ 2
 v = a * t + vo
 r = a * (t ^ 2/2) + vo * t + ro
 r = (2) * ((3 ^ 2) / (2)) + (0) * (3) + (0) = 9 m
 
 the length of the plane is 9m

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