68P. A 5.00 kg block is pulled along a horizontal frictionless floor by a cord that exerts a force F= 12.ON at an angle 6= 25.0 above the horizontal, as shown in Fig. 5-57. (a) What is the acceleration of the block? (b) The force F is slowly increased. What is its value just before the block is lifted (completely) off the floor? (c) What is the acceleration of the block just before it is lifted (completely) off the floor? %3D 5.00 25.0 kg

Redo Example 5, assuming that there is no upward lift on the plane generated by its wings. Without such lift, the guideline slopes downward due to the weight of the plane. For purposes of significant figures, use 2.91 kg for the mass of the plane, 12.2 m for the length of the guideline, and 18.2 and 36.4 m/s for the speeds. (a) Number (b) Number Units Units

(a) A 1 kg block of wood sits on a 30 degree incline. If an applied force of 10 N causes the block to accelerate up the ramp at 0.5 m/s^2 what is the force of friction between the block and the ramp. [K___/4] A

ODI 48. (II) A small box is held in place against a rough vertical wall by someone pushing on it with a force directed upward at 28° above the horizontal. The coefficients of static and kinetic friction between the box and wall are 0.40 and 0.30, respectively. The box slides down unless the applied force has magnitude 23 N. What is the mass of the box? 49. (II) Two crates, of mass 65 kg and 125 kg, are in contact and at rest on a horizontal surface (Fig. 4-57). A 650-N force is exerted on the 65-kg crate. If the coefficient of kinetic friction is 0.18, calculate (a) the acceleration of the sys- tem, and (b) the force that each crate exerts on the other. (c) Repeat with the crates reversed. 650 N 65 kg 125 kg FIGURE 4-57 Problem 49. 50. (II) A person pushes a 14.0-kg lawn mower at constant speed with a force of F = 88.0 N directed along the handle, which is at an angle of 45.0° to the horizontal (Fig. 4-58). the bed of abou 56. (II) A erates c impedi friction 57. (II) Th m FIGURE 4-5…