Solving for Distance and Time: Motion on Incline Homework Help

[kboykb]

Homework Statement

A ball is allowed to roll from rest down an inclined plane, and the distances are marked every 1.6 s. If the second mark is made 1.4 m from the starting point, where is the first mark?

Where is the Fourth Mark?

Homework Equations

x=kt^2 .. k is the constant that I need to figure out to answer the questions.

t = 4 x 1.6s for the 2nd part of the question

The Attempt at a Solution

I'm confused with what variables to plug in in order to answer the question.

t is obviously 1.6s, but I don't know the X.
1.4 = k1.6^2 = 1.4 = k2.56 ... 1.4 / 2.56 = k .. 0.55 = k .. Not correct. I need this K in order to find the solution to the 2nd problem

 

[Delphi51]

Welcome to PF!

I think the ball will roll with constant acceleration so your x = kt² should be right. Very clever of you to see that, or guess it.

You are interested in two sets of data:
1) d = ?, t = 1.6
2) d = 1.4, t = 3.2
In the second one, you know both d and t so you can plug them into the formula and find the k. Then apply the formula with the known value of k to the first set to find its d.

 

[kboykb]

Thanks for the help Delphi! :) (Sorry for my lateness, but wanted to show my gratitude)