Problem: A truck is stopped at a stop light on a street in San Francisco with an 18% grade (a 10° incline), facing down the incline. A distracted driver driving a sedan down the same road does not notice the red light, nor the truck, and collides with the back of the truck at full speed. The car and truck stick together after the collision and slide to a stop down the road. The police investigating the accident want to know if the car was going above the speed limit, set at 25 miles per hour. The police determine that the car and truck slid a distance of 4 m together after the collision. Determine if the car was speeding before it collided with the truck. A typical mass for a sedan is 1400 kg, while a truck has a mass of 2000 kg. The coefficient of kinetic friction between car tires and dry pavement is 0.6.

Problem Details

A truck is stopped at a stop light on a street in San Francisco with an 18% grade (a 10° incline), facing down the incline. A distracted driver driving a sedan down the same road does not notice the red light, nor the truck, and collides with the back of the truck at full speed. The car and truck stick together after the collision and slide to a stop down the road. The police investigating the accident want to know if the car was going above the speed limit, set at 25 miles per hour. The police determine that the car and truck slid a distance of 4 m together after the collision. Determine if the car was speeding before it collided with the truck. A typical mass for a sedan is 1400 kg, while a truck has a mass of 2000 kg. The coefficient of kinetic friction between car tires and dry pavement is 0.6.

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