EXERCISES On Application Of Newton 2nd Law 1st Part

EXERCISES on Application of Newton 2nd Law-(1st PART)
56. Two boats pull a 75.0-kg water skier, as illustrated in Fig. 4.32. (a) If each boat pulls with a force of 600 N and the skier travels at a constant velocity, what is the magnitude of the retarding force between the water and the skis? (b) Assuming that the retarding force remains constant, if each boat pulls with a force of 700 N, what is the magnitude of the acceleration of the skier?

Figure 4.32 Double tow. See Exercise 56.
57. (a) A 65-kg water skier is pulled by a boat with a horizontal force of 400 N due east with a water drag on the skis of 300 N. A sudden gust of wind supplies another horizontal force of 50 N on the skier at an angle of north of east. At that instant, what is the skier’s acceleration? (b) What would be the skier’s acceleration if the wind force were in the opposite direction to that in part (a)?
58. A boy pulls a box of mass 30 kg with a force of 25 N in the direction shown in Fig. 4.33. (a) Ignoring friction, what is the acceleration of the box? (b) What is the normal force exerted on the box by the ground?

Figure 4.33 Pulling a box. See Exercises 58 and 89.

89. In Exercise 58 and Fig. 4.33, if the coefficient of kinetic friction between the box and the surface is 0.03 (waxed wood box on snow), what is the acceleration of the box?

59. A girl pushes a 25-kg lawn mower as shown in Fig. 4.34. If and (a) what is the acceleration of the mower, and (b) what is the normal force exerted on the mower by the lawn? Ignore friction.

Figure 4.34 Mowing the lawn. See Exercise 59.
66. Three blocks are pulled along a frictionless surface by a horizontal force as shown in Fig. 4.35. (a) What is the acceleration of the system? (b) What are the tension forces in the light strings? (Hint: Can equal Investigate by drawing free-body diagrams of each block separately.)

Figure 4.35 Three-block system. See Exercises 66 and 95.
95. For the system illustrated in Fig. 4.35, if and between the blocks and the surface, what applied forces will (a) set the blocks in motion and (b) move the blocks at a constant velocity?

67. Assume ideal conditions for the apparatus illustrated in Fig. 4.36. What is the acceleration of the system if (a) and and (b) and

Figure 4.36 Which way will they accelerate? See Exercises 67, 97, and 98.
97. For the apparatus in Fig. 4.36, what is the minimum value of the coefficient of static friction between the block and the table that would keep the system at rest if , and (Assume ideal conditions for the string and pulleys.)

98. If the coefficient of kinetic friction between the block and the table in Fig. 4.36 is 0.560, and and (a) what shouldbe if the system is to move with a constant speed? (b) If what is the magnitude of the acceleration of the system? (Assume ideal conditions for the string and pulleys.)

96. In the apparatus shown in Fig. 4.43, and the coefficients of static and kinetic friction between and the table are 0.60 and 0.40, respectively. (a) What mass of will set the system in motion? (b) After the system moves, what is the acceleration?

Figure 4.43 Friction and motion. See Exercise 96.
68. The Atwood machine consists of two masses suspended from a fixed pulley, as shown in Fig. 4.37. It is named after British scientist George Atwood (1746–1807), who used it to study motion and to measure the value of g. If and (a) what is the acceleration of the system, and (b) what is the magnitude of the tension in the string?

Figure 4.37 Atwood machine. See Exercises 68, 69 and 70

69. An Atwood machine (see Fig. 4.37) has suspended masses of 0.25 kg and 0.20 kg. Under ideal conditions, what will be the acceleration of the smaller mass?

70. One mass, , of an ideal Atwood machine (see Fig. 4.37) rests on the floor 1.10 m below the other mass, (a) If the masses are released from rest, how long does it take to reach the floor? (b) How high will mass ascend from the floor? [Hint: When hits the floor, continues to move upward.]

72. In the ideal apparatus shown in Fig. 4.38, What is if both masses are at rest? How about if both masses are moving at constant velocity?

Figure 4.38 Inclined Atwood machine. See Exercises 72, 73, and 99.
73. In the ideal setup shown in Fig. 4.38, and (a) What is the acceleration of the masses? (b) What is the tension in the string?

99. In the apparatus shown in Fig. 4.38, and the coefficients of static and kinetic friction between and the inclined plane are 0.30 and 0.20, respectively. (a) What is if both masses are at rest? (b) What is if both masses are moving at constant velocity? Neglect all friction.