Question

A driver is driving once again from Nogales to Tucson on I-19. Suddenly a roadrunner darts out into the middle of the road. It doesn’t see her at first, because it is focused on a tasty lizard it’s trying to catch. She is initially traveling at 110 km/hour, the roadrunner is 30m in front of her when she applies her brakes, and the brakes decelerate the car at 9 m/s2.

She slams on her brakes, and the sound of squealing brakes alerts the bird to the onrushing car. Being an agile critter, it hops out of the way, squawking irately that its meal has been disturbed.

Hint: You will need the quadratic formula for this problem.

(a) Graph the position vs. time of the car, and label the position of the roadrunner on the graph.

(b) How long does the roadrunner have to get out of the car’s way?

(c) The quadratic formula gives you two solutions to the quadratic. Which one is the physically meaningful answer? What does the other solution mean, if anything?

Answer 1