Physics problem help?

You are driving to the grocery store at 20 m/s. You are 110 m from an intersection when the traffic light turns red. Assume that your reaction time is 0.50 s and that your car brakes with constant acceleration.



How far are you from the intersection when you begin to apply the brakes?

__________m

What acceleration will bring you to rest right at the intersection?

__________m/s

How long does it take you to stop after the light changes?

__________s

Physics problem help?How far do you travel during the reaction time.



d = Vt = 20 * .5 = 10 m



Therefore, you were originally 110 m away so now you are 100 - 10 = 100 m away from the intersection when you apply the brakes.



Find the time it would take to stop (where Vf = 0).



a = (Vf - V0)/t = -V0/t



d = V0*t + 1/2 at虏

d = V0*t + 1/2 (-V0/t)*t虏

d = V0*t + 1/2*-V0*t

d = 1/2 V0*t

t = 2d/V0

t = (2*100)/20 = 10 s



What is the acceleration



a = -V0/t = -20/10 = -2 m/s虏