Table of contents X Search this book 6 Applications of Newton's Laws 6.1 Solving Problems with Newton's Laws Introduction 25. A 30.0-kg girl in a swing is pushed to one side and held at rest by a horizontal force IF so that the swing 6.1 Solving Problems with ropes are 30.0" with respect to the vertical. (a) Calculate the tension in each of the two ropes supporting the Newton's Laws swing under these conditions. (b) Calculate the magnitude of F. 6.2 Friction 6.3 Centripetal Force 26. Find the tension in each of the three cables supporting the traffic light if it weighs 2.00 x 102 N. 6.4 Drag Force and Terminal Speed 41.00 63.0 Chapter Review Key Terms 1 1 T 2 Key Equations Summary Conceptual Questions T3 Problems Additional Problems Challenge Problems $7 Work and Kinetic Energy 8 Potential Energy and Conservation of Energy 9 Linear Momentum and Collisions 10 Fixed-Axis Rotation 11 Angular Momentum 12 Static Equilibrium and Elasticity 13 Gravitation W = 200 N 14 Fluid Mechanics Waves and Acoustics A | Units B | Conversion Factors 27. Three forces act on an object, considered to be a particle, which moves with constant velocity C | Fundamental Constants v = (31 - 2j) m/s. Two of the forces are F1 = (31 + 5j ) N and F2 = (4i - 7j ) N. Find the third force.39. A student's backpack, full of textbooks, is hung from a spring scale attached to the ceiling of an elevator. When the elevator is accelerating downward at 3.3 [El/'32, the scale reads 50 N. {a} What is the mass of the backpack? [b] What does the scale read it the elevator moves upward while speeding up at a rate 3.8 mfs? {c} What does the scale read if the elevator moves upward at constant velocity? (d) It the elevator had no brakes and the cable supporting it were to break loose so that the elevator could fall freely, what would the spring scale read? 42. The device shown below is the Atwood's machine considered in Example 6.5 . Assuming that the masses of the string and the frictionless pulley are negligible, (a) find an equation for the acceleration of the two blocks; {b} find an equation for the tension in the string; and {c} find both the acceleration and tension when block 1 has mass 2.00 kg and block 2 has mass 4.011] kg. 43. Two blocks are connected by a massless rope as shown below. The mass of the block on the table is 4.0 kg and the hanging mass is 1.0 kg. The table and the pulley are frictionless. (a) Find the acceleration of the system. to) Find the tension in the rope. {c} Find the speed with which the hanging mass hits the oor it it starts from rest and is initially located 1 .t] m from the oor. 45. A 2.00 kg block {mass 1} and a 4.00 kg block {mass 2} are connected by a light string as shown; the inclination of the ramp is 40.0" . Friction is negligible. What is [a] the acceleration of each block and (b) the tension in the string? 61. Consider the 52.0kg mountain climber shown below. {a} Find the tension in the rope and the force that the mountain climber must exert with her feet on the vertical rock face to remain stationary. Assume that the force is exerted parallel to her legs. Also, assume negligible foroe exerted by her arms. [b] What is the minimum coefficient of friction between her shoes and the cliff? 63. The contestant now pulls the block of ice with a rope over his shoulder at the same angle above the horizontal as shown below. The coefficient of friction of ice can be found in Table 6.1 . Calculate the minimum force F he must exert to get the block moving. (b) What is its acceleration once it starts to move, if that force is maintained? 250T3. A child of mass 40.0 kg is in a roller coaster ear that travels in a loop of radius 7.00 m. At point A the speed of the ear is 10.0 mfs. and at point B. the speed is 10.5 ma's. Assume the child is not holding on and does not wear a seat belt. (a) What is the force of the car seat on the child at point A? [b] What is the force of the ear seat on the child at point B? {e} What minimum speed is required to keep the child in his seat at point A