A 100 N force applied by the brakes stops a car traveling at an initial velocity of 25 km/ hr. Solve for mass.
_
I'm getting a negative mass, so I must be doing something wrong.
$\displaystyle v = V_0 t + 1/2 a t^2$
$\displaystyle
0= (6.94 m/s * 15 seconds) + (.5)(a)(15)^2$
$\displaystyle 104.1 + 125a$
Which simplifies to $\displaystyle -.93 m/s$
I plug that into $\displaystyle F= ma$
so...
$\displaystyle 100= (m)(-.93)$
Which comes out to -107.53