(II) A small box is held in place against a rough verticalwall by someone pushing on it with a force directed upwardat 28° above the horizontal. The coefficients of static andkinetic friction between the box and wall are 0.40 and0.30, respectively. The box slides down unless the appliedforce has magnitude 23 N. What is the mass of the box?

(II) The cable supporting a 2125-kg elevator has a maximumstrength of 21,750 N. What maximum upward accelerationcan it give the elevator without breaking?

(II) A 12.0-kg monkey hangs from a cord suspended fromthe ceiling of an elevator. The cord can withstand a tensionof 185 N and breaks as the elevator accelerates. Whatwas the elevator’s minimum acceleration (magnitude anddirection)?

(II) A train locomotive is pulling two cars of the same mass behind it, Fig., 4–51. Determine the ratio of the tension in the coupling (think of it as a cord) between the locomotive and the first car (Fr1), to that between the first car and the second car (Fr2), for any nonzero acceleration of the train. Car 2 Car 1 FIGURE 4–51 Problem 27.

(II) What will a spring scale read for the weight of a 58.0-kgwoman in an elevator that moves (a) upward with constantspeed (b) downward with constant speed 5.0 m/s(c) with an upward acceleration 0.23 g, (d) with a downwardacceleration 0.23 g, and (e) in free fall?

(III) A person jumps from the roof of a house 2.8 m high.When he strikes the ground below, he bends his knees sothat his torso decelerates over an approximate distance of0.70 m. If the mass of his torso (excluding legs) is 42 kg,find (a) his velocity just before his feet strike the ground,and (b) the average force exerted on his torso by his legsduring deceleration.

(I) A box weighing 77.0 N rests on a table. A rope tied to the box runs vertically upward over a pulley and a weight is hung from the other end (Fig. 4–45). Determine the force that the table exerts on the box if the weight hanging on the other side of the pulley weighs (a) 30.0 N, (b) 60.0 N, and (c) 90.0 N. FIGURE 4-45 Problem 20.

(I) A force of 35.0 N is required to start a 6.0-kg box moving across a horizontal concrete floor. (a) What is the coefficient of static friction between the box and the floor? (b) If the 35.0-N force continues, the box accelerates at 0.60 m/s What is the coefficient of kinetic friction?

(a) A 5.5 kg salami is supported by a cord that runs to a spring scale, which is supported by another cord from the ceiling . What is the reading on the scale, which is marked in SI weight units? (This is a way to measure weight by a deli owner.) N(b)  the salami is supported by a cord that runs around a pulley and to a scale. The opposite end of the scale is attached by a cord to a wall. What is the reading on the scale? (This is the way by a physics major.) N(c)  the wall has been replaced with a second 5.5 kg salami on the left, and the assembly is stationary. What is the reading on the scale? (This is the way by a deli owner who was once a physics major.) N