A woman hits her car brakes in a panic stop and decelerates at a rate of 5 m/s^2 . The car comes to rest at a distance of 62.5 meters from the point where she first applied her brakes. How fast was she traveling when she hit her brakes?

Question

matt101 · Answer

You're given acceleration (a) and distance (d) directly, but also final velocity (vf) - the car comes to a stop, so vf=0.

You're given this information and asked to find initial velocity (vi). That means you can use this equation to find the answer:

$$v_f^2=v_i^2+2ad$$

anonymous · Answer

I think -25m/s is the right answer now. Thanks.

matt101 · Answer

No negative but otherwise I agree! (The acceleration is negative, so that cancels out the negative when you transpose the 2ad to the other side. You also can't take the square root of a negative number!)