The question is whether a driver is exceeding a 30 miles/hr speed limit before he makes an emergency stop. The length of the skid marks on the road is 19.2 feet. The police assumed that the maximum deacceleration of the car would not exceed the acceleration of a freely falling body and arrested the driver for speeding. Was this correct to do?(adsbygoogle = window.adsbygoogle || []).push({});

So the acceleration of a freely falling body is [itex] a = -32 \frac{ft}{sec^{2}} [/itex]. So [itex] v_{x}^{2} = v_{x}_{0}^{2} + 2a_{x}(x-x_{0}}) [/itex]. Since [itex] v_{x} = 0 [/itex], [itex] 0 = v_{x}_{0}^{2} - 64(19.2) [/itex]. So [itex] v_{x}_{0}^{2} = 1228.8 [/itex] and [itex] v_{x}_{0} = 35 [/itex]. So he was speeding. Is this correct?

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Police Problem

**Physics Forums | Science Articles, Homework Help, Discussion**