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## Main Question or Discussion Point

Suppose a particle is moving along the $x$ axis with velocity $v$. It starts at the point $-5$ and has constant negative acceleration $a$.

You need to find what time the particle reaches the origin.

My teacher solved this question, and used the kinematics equation Δx = v_0t+1/2 at^2

The quadratic had two roots, one of which was negative. What does the negative root mean? Is it extraneous (my teacher just said to ignore it)?

Thanks.

You need to find what time the particle reaches the origin.

My teacher solved this question, and used the kinematics equation Δx = v_0t+1/2 at^2

The quadratic had two roots, one of which was negative. What does the negative root mean? Is it extraneous (my teacher just said to ignore it)?

Thanks.