11. An astronaut in orbit with a mass of 70 kg pushes a box with a mass of 90 kg. The force the astronaut exerts is 630 N against the space junk. What is the acceleration of the astronaut and the space junk? 12. An unseen wrestler with a mass of 114 kg is in an elevator standing on a scale. Draw free-body-diagram for each scenario and nd the normal force (the scale reading) when: a. The elevator is moving up at a constant velocity b. The elevator is accelerating up at 2 m/s2 c. The elevator is decelerating up at 3 m/s2 13. A student presses a book against a vertical wall. If the book has a mass of 6 kg, what must the friction be to prevent the book from sliding down the wall? Draw the force diagram 14. A 70 kg box is pulled by a person with a 300 N force at an angle of 30 above the horizontal. The frictional force is 140 Newtons. a. What is the vertical force caused by the person? b. What is the horizontal force caused by the person? 0. Draw a quantitative force diagram!! (1. Find the acceleration of the box in the horizontal direction. e. Find the normal force on the box (vertical acceleration should equal 0) 15. Two objects are connected with a m, -1- M2 _, r' weightless string. One of them has a mass m1 = 20 kg, the other one has a mass of m2 = 30 kg. A force of 50 N is applied to the 30 kg one. What is the acceleration of the system if there is no friction? 16. Two objects are connected with a m, T mz -'r' weightless string. One of them has a mass m1 = 20 kg, the other one has a mass of m2 = 30 kg. A force of 50 N is applied to the 30 kg one. What is the tension in the rope if there is no friction? Forces and Newton's Laws 1. What is the weight a 50 kg firefighter? 2. What acceleration will you give to a 24.3 kg box if you push it horizontally with a net force of 85.5 N? 3. A 2 kg mass is pushed along a horizontal frictionless surface by a 3 N force which is parallel to the surface. The weight of the mass is approximately 4. A 15-N force and a 45-N force act on an object simultaneously. Draw the FBD and find the net force on the object if the forces are a. in opposite directions b. in the same direction c. perpendicular to each other 5. What is the gravitational acceleration on a planet where a 2 kg mass has a weight of 16 N on the planet's surface? 6. Base your answer on the graph below which JE VELOCITY (m/ s) represents the velocity-time 01 2 4 5 6 7 8 9 10 11 12 TIME ( seconds) relationship for a 2.0 kg mass moving along a horizontal surface. What is the net force on the mass during the different time intervals (AB, BC, CD, DE, EF) 7. What is the weight of an object on the Moon (gravity on moon = 1.63m/s') if its weight on Earth is 100 N? 8. Two frictionless blocks, having masses of 8.0 kg and 2.0 kg, rest on a horizontal surface. If a force applied to the 8 kg block gives it an acceleration of 5.0 m/s, then the same force will give the 2 kg block an acceleration of? 9. A child pulls a wagon with a 12 N horizontal force. If the wagon experiences 2 N of friction and has a mass of 10 kg, what is the acceleration of the wagon? 10. What force must be applied on a 16.2 N stone to make it accelerate upward in 2.3 m/s2