Max Acceleration for Car w/o Cup Sliding: 2.35 m/s^2

[dg_5021]

Problem-
If the coefficient of static friction between the coffee cup and the roof of the car is 0.24, What is the maximum acceleration the car can have without causing the cup to slide? Ignore the effects of air resistance.

Answer-
i know the formula is: Fs= (ms) (N)
i multipy 0.24 x 9.81m/s^2
and got =2.35 m/s^2

Did i do it right? Is my work correct? please help

 

[HallsofIvy]

There is a rather important piece of information missing here! Remember what "N" is?

Don't you think a coffee cup made of lead would be less likely to slide than one made of fine china?

 

[dg_5021]

i know N= (m)(g)
but the question never gives me the kg and i know gravity =9.81m/s^2

am i suppose to find kg?

 

[dg_5021]

oh wait i got it ms= Fs/N
ms=m(ax)/m(g)
ms=ax/g
ms x g=ax
.24x 9.81 = 2.35m/s^2

thanks