What Is the Static Coefficient of Friction Between the Object and the Dash?

[curiousgeorge99]

Homework Statement

An object is on the dash of a car and it slides forward when the driver decelerates from 50 km/h to 0 in 3.0s or less. If the driver decelerates over a longer time it doesn't slide. What is the static coefficient?

Homework Equations

I'm not sure. I have tried several but I feel like every equation has two unknowns. If I use v=vi + at I can get acceleration. But, then what? I don't have a mass, and it seems that I need that for F=MA, or F=mg, or to figure out Fn.

The Attempt at a Solution

I've figured out the Acceleration by using v=vi + at. I can figure out the distance traveled in 3.0s by using x=x1 + Vxt + 0.5gt~2. But without mass, I don't know what else to calculate.

 

[e(ho0n3]

Suppose you do know the mass; call it m. What would you have as an answer?