## Physics

Case Study Information:

An accident occurred in which Driver 1 turned right from Post Road onto the eastbound lane of Route 460.  Driver 2 was approaching this same intersection on Route 460 traveling east.  Driver 2 swerved left to avoid hitting Driver 1, passing driver 1, and then stopping ahead of driver 1.  Driver 1 passed the now stopped car of Driver 2 and pulled onto the shoulder of Route 460 east of Driver 2.  Police arrived and details for the accident were gathered.

Driver 2’s car stopped a distance of 325 feet east of Post Road.  Driver 1 stopped 50 feet east of Driver 2’s car.  Driver 1’s car was a 2018 Jeep Grand Cherokee.  Driver 2’s car was a 2018 Honda Fit.

Road conditions were dry, the road at this point is straight and level.  No other cars were affected by the incident.

Driver 1’s version: Driver 1 said he pulled out while Driver 2 was still some distance west of the intersection and that Driver 1 had accelerated to 50 MPH before Driver 2 swerved around him, evidently going well over the speed limit for Route 460, which is 60 MPH.  Had Driver 2 not been speeding, he would have been able to slow and not swerve.

Driver 2’s version: Driver 2 said he was driving at 60 MPH and Driver 1 pulled onto Route 460 when Driver 2 was only 2 car length’s from the intersection, forcing Driver 2 to swerve to avoid a collision.  Driver 1 had barely started to accelerate and could not have been going 50 MPH when Driver 2 had to swerve around Driver 1.  He started his swerve one car-length behind Driver 1 and started to stop when he was one car-length

in front of Driver 1.

• Based on a test of acceleration for all vehicles, a 2018 Jeep Grand Cherokee model can accelerate from zero to 60 MPH in 8.6 seconds.
• Based on tests of stopping distance, the Honda Fit can brake from 60 MPH to a stop in a distance of 131 feet.
• Consider a car length to be 15 feet.

It may be useful to do calculations in units of feet/second rather than miles/ hour.  The conversion rate is 1 MPH = 1.467 ft/s so 50 mph = 73.3 ft/s and 60 mph = 88 ft/s.