Newtons second law and stopping on a dime

[ledhead86]

An advertisement claims that a particular automobile can "stop on a dime." What net force would actually be necessary to stop an automobile of mass (m) traveling initially at a speed of (v) in a distance equal to the diameter of a dime, which is (d) ?

 

[ledhead86]

Σ F = -f = m*a

I used the formula v2 = v_02 + 2a(x-x_0) to find the acceleration

so a = (v2 – v_02) / 2(x-x_0) = ((0)2 – (v)2) / 2( d – 0)

then my final answer would be ((0)2 – (v)2) / 2( d – 0) * mass

 

[ledhead86]

but apparently this is incorrect. What am I doing wrong?

 

[Doc Al]

Looks OK to me. (Simplify the final expression, of course.)

 

[Doc Al]

but apparently this is incorrect. What am I doing wrong?

What makes you think this is incorrect? Also: Just find the magnitude of the force.

 

[ledhead86]

nevermind, it was correct. I incorrectly typed it in the program