A person driving on I-82 glanced at his phone to read a very important text message. When he looked back up at the road, he saw that the traffic ahead had come to a standstill and he immediately slammed on his brakes. His car created 96.5 m long skid marks before rear-ending another car. Unfortunately, a passenger in the rear-ended car was seriously injured, thus requiring an investigation by the State Patrol. The State Patrol has no proof of distracted driving, however they want to determine if a citation for speeding should be issued. A State Patrol investigator used a 3.9 kg drag sled to determine the coefficient of kinetic friction between the road and the tires of the car. The drag sled’s spring scale read 28 N when it was pulled along the ground at a constant speed. Use Newton’s Second Law and kinematics to estimate the minimum value of the car’s speed when the driver locked the brakes. (answer: about 83 mi/hr) Note: You do not need the mass of the car to answer this question. FNET = ma fk = kN W = mg g = 9.81 m/s2 v2 = v02 + 2ax 1 mi/hr = 0.45 m/s
A person driving on I-82 glanced at his phone to read a very important text message. When he looked back up at the road, he saw that the traffic ahead had come to a standstill and he immediately slammed on his brakes. His car created 96.5 m long skid marks before rear-ending another car. Unfortunately, a passenger in the rear-ended car was seriously injured, thus requiring an investigation by the State Patrol. The State Patrol has no proof of distracted driving, however they want to determine if a citation for speeding should be issued.
A State Patrol investigator used a 3.9 kg drag sled to determine the coefficient of kinetic friction between the road and the tires of the car. The drag sled’s spring scale read 28 N when it was pulled along the ground at a constant speed.
Use Newton’s Second Law and
Note: You do not need the mass of the car to answer this question.
FNET = ma fk = kN W = mg g = 9.81 m/s2
v2 = v02 + 2ax 1 mi/hr = 0.45 m/s
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