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### Homework 14 Due 12/13/10

 Needed info: -Newton’s 2nd Law.  F=ma           -force equals mass times acceleration          -force is measured in Newtons (N)          -mass is measured in kilograms (KG)          -acceleration is measured in meters per second squared (m/s2) -The force of gravity is 1g, or 9. m/s2     1. A little boy pushes a wagon with his dog in it. The mass of the dog and wagon together is 45 kg. The wagon accelerates at 0.85 m/s2. What force is the boy pulling with?   2. A 1650 kg car accelerates at a rate of 4.0 m/s2. How much force is the car's engine producing?   3. A 68 kg runner exerts a force of 59 N. What is the acceleration of the runner?   4. A crate is dragged across an ice covered lake. The box accelerates at 0.08 m/s2 and is pulled by a 47 N force. What is the mass of the box?   5. 3 women push a stalled car. Each woman pushes with a 425 N force. What is the mass of the car if the car accelerates at 0.85 m/s2?   6. A tennis ball, 0.314 kg, is accelerated at a rate of 164 m/s2 when hit by a professional tennis player. What force does the player's tennis racket exert on the ball?   7. In an airplane crash a woman is holding an 8.18 kg, 18 pound, baby. In the crash the woman experiences a horizontal de-acceleration of 88.2 m/s2. How many g's is this de-acceleration? How much force must the woman exert to hold the baby in place?   8. When an F-14 airplane takes-off an aircraft carrier it is literally catapulted off the flight deck. The plane's final speed at take-off is 68.2 m/s. The F-14 starts from rest. The plane accelerates in 2 seconds and has a mass of 29,545 kg. What is the total force that gets the F-14 in the air?   9. A sports car accelerates from 0 to 60 mph, 27 m/s, in 6.3 seconds. The car exerts a force of 4106 N. What is the mass of the car?   10. A sled is pushed along an ice covered lake. It has some initial velocity before coming to a rest in 15 m. It took 23 seconds before the sled and rider come to a rest. If the rider and sled have a combined mass of 52.5 kg, what is the magnitude and direction of the stopping force? What do "we" call the stopping force?