Ball rolling off an inclined plane

[Avathacis]

Homework Statement

A ball is rolling off an inclined plane. After 1 second the ball has traveled 10cm. How far will it travel in 3 seconds?

Homework Equations

v = l/t
v = v0t + at
x = x0 + v0t + at²/2

The Attempt at a Solution

v = l/t₁

v = v0t + at (there's no starting velocity, so)

l/t₁ = at₁

l = at²₁

a = l/t²₁

l₃ = x0 + v0t + at²/2

l₃ = at²/2

l₃ = (l/t²₁ + t²) 1/2

l₃ = 0.45m

The answer should be 0.9m, so i guess I'm supposed to lose the 1/2 somewhere.

 

[Doc Al]

v = l/t

This only applies if the speed is constant, which is not the case here.

x = x0 + v0t + at²/2

Use this to figure out the acceleration.

 

[Avathacis]

This only applies if the speed is constant, which is not the case here.


Use this to figure out the acceleration.

Thanks! Done!