You are driving North through an intersection in a 55 $mi/hr$ speed zone, when t

Question

You are driving North through an intersection in a 55 $mi/hr$ speed zone, when the local Chief of Police, who is driving his new Cadillac and approaching the intersection from the West, hits you broadside. The two cars stick together and skid a distance 38.6 $m$ with locked wheels at an angle of 61.8° to the East of North. The mass of your car is 1517.0 $kg$ while the Cadillac has a mass 2054.0 $kg$. The coefficent of sliding friction is 0.60. The Chief of Police is angry that you have damaged his new Cadillac and gives you a ticket for speeding. The local judge is going to believe his Chief of Police rather than some out-of-town student. You realize that the knowledge you learned in your physics course is your only hope for acquittal. Compute the speed of the Chief of Police immediately prior to the collision. Use conservation of momentum. Submit Answer Incorrect. Tries 3/8 Previous Tries Compute your speed immediately prior to the collision as evidence for or against the speeding ticket.

Explanation / Answer

The frictional work reduces the kinetic energy of the combined cars to 0

so *(M+m)*g*x = 1/2(*M+m)*v^2

so v(after collision) = sqrt(2**g*x) = sqrt(2*0.60*9.8*38.6) = 21.30m/s

Let East be x direction

so from conservation of momentum in the x (The chief momentum = x component of the combined momentum)

M*v = (M + m)*v(after)*sin(61.8)

so v(Police car) = (M + m)*v(after)*sin(61.8)/M = (1517 + 2054)*21.30*sin(61.8)/2054 = 32.64m/s

This = 32.64/0.447 = 73.02mph

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.