9. Erika is on an elevator and presses the button to go down. When the elevator first starts moving, it has an acceleration of 2.5 m/s downward. Erika and the elevator have a combined mass of 1250 kg. a. Draw a free-body diagram for the elevator. b. What is the tension in the cable that. provides the upward force on the elevator car? 10. Ngan has a weight of 314.5 N on Mars and a weight of 833.0 N on Earth. a. What is Ngan's mass on Mars? b. What is the acceleration due to gravity on Mars, 11. Alex is on the wrestling team and has a - mass of 85.3 kg. Being a whiz at physics, he realizes that he is over the 830.0-N cut- off for his weight class. If he can convince the trainers to measure his weight in the elevator, what must be the acceleration of the elevator so that he just makes hist weight class? 12. During a space launch, an astronaut typi- cally undergoes an acceleration of 3 gs which means he experiences an accelera- tion that is three times that of gravity alone. What would be the apparent weight of a 205-kg astronaut that experiences a 3-g liftoff? 13. Alfonso and Sarah like to go sky diving together. Alfonso has a mass of 88 kg. and Sarah has a mass of 66 kg. While in free fall together, Alfonso pushes Sarah hori- zontally with a force of 12.3 N. a. What is Alfons's horizontal acceleration? b. What is Sarah's horizontal acceleration? 14. A 7.25-g bullet is fired from a gun. The muzzle velocity of the bullet is 223 m/s.. Assume that the bullet accelerates at a constant rate along the barrel of the gun before it emerges with constant speed. The barrel of the gun is 0.203 m long. What average force does the bullet exert on the gun? 15. A 15.2-kg police battering ram exerts an average force of 125 N on a 10.0-kg door. a. What is the average acceleration of the door! b. What is the average acceleration of the --- battering ram? 16. As a demonstration, a physics teacher attaches a 7.5-kg object to the ceiling by a nearly massless string. This object then supports a 2.5-kg object below it by anoth- er piece of string. Finally, another piece of string hangs off the bottom of the lower. object to be pulled with ever increasing force until the string breaks somewhere. The string will break when the tension reaches 156 N.. a. Which length of string will break first? b. What is the maximum downward force the physics teacher can apply before the string breaks? 7.5 kg 2.5 kg 3. Draw a free-body diagram for a submerged beach ball as it rises toward the surface just after being released. Identify the forces act ing on the beach ball and indicate the direc tion of the net force and the acceleration. 4. Muturi is rearranging some furniture. He pushes the dresser with a force of 143 N, and there is opposing frictional force of 112 N. What is the net force? 5. One of the floats in a Thanksgiving Day parade requires four people pulling on ropes to maintain a constant speed of 3.0 km/h for the float. Two people pull with a force of 210 N each, and the other two pull with a force of 140 N each. a. Draw a free-body diagram. b. What is the force of friction between the float and the ground? 6. Five people are playing tug-of war. Anders and Alyson pull to the right with 45 N and 35 N, respectively. Calid and Marisol pull to the left with 53 N and 38 N, respectively With what force and in what direction does Benito pull if the game is tied? ** 7. Two dogs fight over a bone. The larger of the two pulls on the bone to the right with a force of 42 N. The smaller one pulls to the left with a force of 35 N. a. Draw the free-body diagram for the bone. b. What is the net force acting on the bone? c. If the bone has a mass of 2.5 kg, what is its acceleration? Dog 1 Dog 2 8. A large model rocket engine can produce a thrust of 12.0 N upon ignition. This engine is part of a rocket with a total mass of 0.288 kg when launched. a. Draw a free-body diagram of the rocket just after launch. b. What is the net force that is acting on the model rocket just after it leaves the ground? C. What is the initial acceleration of the rocket?