mass and stopping distance and time

[MedGrl@2022]

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I am reviewing some EK problems today and according to some friction problems. Mass is independent of stopping distance and time in a car for example. I see from he practice problems that mass cancels out. However, this seems counter-intuitive to me as mass is the inertial component and isn't it harder to stop something with greater inertia?

 

[milski]

I am reviewing some EK problems today and according to some friction problems. Mass is independent of stopping distance and time in a car for example. I see from he practice problems that mass cancels out. However, this seems counter-intuitive to me as mass is the inertial component and isn't it harder to stop something with greater inertia?

Friction is also proportional to the mass - F_friction=μN=μgm, where N is the normal. So you're stoping something with greater inertia but also using a proportionally greater force.