Answer the practice problems

9. A 2000 kg elephant is charging a hunter at a speed of 7.50 m/s. a. What is the momentum of the elephant? b. What is the momentum of a 0.0400 kg tranquilizer dart fired at a speed of 600 m/s at the elephant? c. What is the momentum of the 85.0-kg hunter running at 7.40 m/s after missing the elephant? 10. A runaway train car that has a mass of 15,000 kg travels at a speed of 5.4 m/s down a track. What is the time required for a force of 1500 N to bring the car to rest? 11. Suppose a child drives a bumper car head on into the side rail, which exerts a force of 4000 N on the car for 0.200 s. a. What impulse is imparted by this force? b. What is the final velocity of the bumper car if its initial velocity was 2.80 m/s and the car plus driver have a mass of 200 kg? (neglect friction between the car and floor.) 12. A 75.0-kg person is riding in a car moving at 20.0 m/s when the car runs into a bridge abutment. What is the average force on the person if he is stopped by an air bag that compresses an average of 15.0 cm