Problem 1: A m = 45 kg crate is placed on an inclined ramp. When the angle that the ramp makes with the horizontal is increased to 0 = 230, the crate begins to slide downward. 1. Draw a free body diagram for the crate on the incline just before it starts to slide and list the forces. 2. What is the coefficient of static friction us between the crate and the ramp? (Give a symbolic and a numerical estimate of the coefficient of static friction). 3. At what angle does the crate begin to slide if its mass is doubled? (explain your answer). Problem 2: Jill of the jungle swings in a circular motion on a vine L = 6.5 m long. When the vine is vertical (at the bottom of the circle), the speed of Jill is v = 2.4 m/s. Jill's mass is m = 61 kg. Give the numerical estimation with 2 significant figures, scientific notation. 1. Calculate the angular speed w of Jill when the vine is vertical (at the bottom of the circle). 2. Draw a free-body diagram of Jill when the vine is vertical (bottom of the circle) and list the forces 3 . Calculate the tension in the vine when the vine is vertical (at the bottom of the circle). 4. What is the apparent weight Wapp of Jill when the vine is vertical (at the bottom of the circle)? Write Wapp as Wapp = (constant) xmg, find the constant. Multiple Choice Questions 1. In the absence of a net force, a moving object will: (a) stop immediately. ( b ) slow down and eventually comes to a stop. (c) move faster and faster. (d) move with constant velocity for a while and then slows to a stop. (e) move with constant velocity. 2. A golf club hits a golf ball with a force of 2400 N. The golf ball hits the club with a force: (a) Slightly less than 2400 N. (b) Exactly 2400 N. (c) Slightly more than 2400 N. (d) Close to O N. (e) Cannot be determined without additional information. 3. Three boxes rest side-by-side on a smooth frictionless, horizontal floor. Their masses are 5.0 kg, 3.0 kg and 2.0 kg, with the 3.0 kg mass in the center. A force of 50 N pushes on the 5.0 kg mass, which pushes against the other two masses. What is the contact force between the 5.0 kg mass and the 3.0 kg mass? 3(a) 5 N. (b) 10 N. (C) 25 N. (d) 40 N. (e) 50 N. 4. It is more difficult to start moving a heavy carton from rest than it is to keep pushing it with constant velocity, because: (a) The normal force is greater when the carton is at rest. (b) The coefficient of static friction is smaller than the coefficient of kinetic friction. (c) Initially, the normal force is not perpendicular to the applied force. (d) The coefficient of static friction is greater than the coefficient of kinetic friction. (e) The coefficient of static friction is equal to the coefficient of kinetic friction. 5. A small metal cylinder rest on a horizontal circular turntable (grey circle), rotating at constant speed as illustrated on the diagram below (top view). Which of the sets of vectors best describes the velocity, acceleration, and net force acting on the cylinder in the diagram below? F V V V V V V a a = 0 a = 0 Fa F a (a) (b) (c) (d) (e) 4