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1. Homework Statement
Your consulting agency, with its extensive knowledge of physics, has been subpoenaed to provide expert testimony at an automobile accident case in civil court. The case involves a crash between a Ford Escort car and a tractortrailer truck.
1. The police department determined that the force required to drag a 130 N (29 lb) car tire across the pavement at a constant velocity is 83 N. Specifications from the truck s manufacturer claim that (for technical reasons) the effective coefficient of friction for truck tires is only 70% that of car tires. What was the coefficient of kinetic friction between the tires and the road for both the car and truck? (Include FBD)
2. After collision, the truck and car skidded at the angles shown in the diagram. The car skidded a distance of 49.8 ft before stopping while the truck skidded 9.5 ft before stopping. (1 ft=.305m) The weight of the car is 13, 600 N and the weight of the truck is 69,700 N. What was the speed of each vehicle just after the collision?
3. The precrash angle between the velocities of the truck and car was 90 degrees. What was the speed of each vehicle just before the collision?
4. At this intersection, the truck driver had a flashing yellow light while the car driver had a flashing red light.
2. Homework Equations
f=mu(N)
w=fd
??
3. The Attempt at a Solution
1. I got .638 and .447 for the coefficients of f for the car and truck respectively.
2. I got 13.88 m/s and 5.09 m/s for v of car and truck respectively.
Don't know how to do 3 and 4.
For 3 I thought it was a conservation of momentum question and tried mv+mv=mv+mv but I really don't know. Please help, thanks! Visual of crash is attached.
Your consulting agency, with its extensive knowledge of physics, has been subpoenaed to provide expert testimony at an automobile accident case in civil court. The case involves a crash between a Ford Escort car and a tractortrailer truck.
1. The police department determined that the force required to drag a 130 N (29 lb) car tire across the pavement at a constant velocity is 83 N. Specifications from the truck s manufacturer claim that (for technical reasons) the effective coefficient of friction for truck tires is only 70% that of car tires. What was the coefficient of kinetic friction between the tires and the road for both the car and truck? (Include FBD)
2. After collision, the truck and car skidded at the angles shown in the diagram. The car skidded a distance of 49.8 ft before stopping while the truck skidded 9.5 ft before stopping. (1 ft=.305m) The weight of the car is 13, 600 N and the weight of the truck is 69,700 N. What was the speed of each vehicle just after the collision?
3. The precrash angle between the velocities of the truck and car was 90 degrees. What was the speed of each vehicle just before the collision?
4. At this intersection, the truck driver had a flashing yellow light while the car driver had a flashing red light.
a.) The car driver claims to have made a full stop at the light before entering the intersection. He also claims that the truck driver did not see him until after the collision. This would make the truck driver partially liable.
b.) The truck driver claims that the car ran the flashing red light. He also claims to have begun braking in anticipation of a collision; traveling at only 6.7 m/s (15 mph) at the moment of impact.
c.) Police measurements show that the distance for the car from the traffic light to the collision point was 13.0 m(42.5 ft) and the distance for the truck from the traffic light to the collision point was 32.8 ft (1ft=.305 m).
d.) Ford Motor Corporation specifications indicate that the maximum acceleration of a comparably loaded Ford Escort is about 3.0 m/s^2, and the maximum acceleration given for the truck is 1.2 m/s^2.
Who is at fault and why?
b.) The truck driver claims that the car ran the flashing red light. He also claims to have begun braking in anticipation of a collision; traveling at only 6.7 m/s (15 mph) at the moment of impact.
c.) Police measurements show that the distance for the car from the traffic light to the collision point was 13.0 m(42.5 ft) and the distance for the truck from the traffic light to the collision point was 32.8 ft (1ft=.305 m).
d.) Ford Motor Corporation specifications indicate that the maximum acceleration of a comparably loaded Ford Escort is about 3.0 m/s^2, and the maximum acceleration given for the truck is 1.2 m/s^2.
Who is at fault and why?
2. Homework Equations
f=mu(N)
w=fd
??
3. The Attempt at a Solution
1. I got .638 and .447 for the coefficients of f for the car and truck respectively.
2. I got 13.88 m/s and 5.09 m/s for v of car and truck respectively.
Don't know how to do 3 and 4.
For 3 I thought it was a conservation of momentum question and tried mv+mv=mv+mv but I really don't know. Please help, thanks! Visual of crash is attached.
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