(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.

(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.

University Physics Volume 1

18th Edition

ISBN:9781938168277

Author:William Moebs, Samuel J. Ling, Jeff Sanny

Publisher:William Moebs, Samuel J. Ling, Jeff Sanny

Chapter5: Newton's Law Of Motion

Section: Chapter Questions

Problem 62P: Consider Figure 5.28. The driver attempts to get the car out of the mud by exerting a perpendicular...

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Consider Figure 5.28. The driver attempts to get the car out of the mud by exerting a perpendicular force of 610.0 N, and the distance she pushes in the middle of the rope is 1.00 m while she stands 6.00 m away from the car on the left and 6.00 m away from the tree on the right. What is the tension Tin the rope, and how do you find the answer?
38. 39. FIGURE 4-53 40 Problems 32 and 33. mB Mass ma rests on a smooth horizontal surface; mg hangs istongi inioq le vertically. ni nworda algne 13.0 kg and mB = 5.0 kg in Fig. 4–53, 33. (II) (a) If mA determine the acceleration of each block. (b) If initially is at rest 1.250 m from the edge of the table, how long does it take to reach the edge of the table if the system is allowed to move freely? (c) If mB must ma be if the acceleration of the system is to be kept at 100 g? 1.0 kg, how large %3D
34. (III) Three blocks on a frictionless horizontal surface are in contact with each other as shown in Fig. 4–54. A force F is applied to block A (mass ma). (a) Draw a free-body dia- gram for each block. Determine (b) the acceleration of the system (in terms of ma, mB, and mc), (c) the net force on each block, and (d) the force of contact that each block exerts on its neighbor. (e) If mĄ = mB = mc = 10.0 kg and F = 96.0 N, give numerical answers to (b), (c), and (d). Explain how your answers make sense intuitively. F MA mB mc FIGURE 4-54 Problem 34.
(II) At the instant a race began, a 65-kg sprinter exerted a force of 720 N on the starting block at a 22° angle with respect to the ground. (a) What was the horizontal acceleration of the sprinter? (b) If the force was exerted for 0.32 s,with what speed did the sprinter leave the starting block?
(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). (a) Draw the free-body diagram showing all forces acting on the mower. Calculate (b) the horizontal friction force on the mower, then (c) the normal force exerted vertically upward on the mower by the ground. (d) What force must the person exert on the lawn mower to accelerate it from rest to 1.5 m/s in 2.5 seconds, assuming the same friction force? F 45° FIGURE 4-58 Problem 50.
(II) (a) A box sits at rest on a rough 33° inclined plane.Draw the free-body diagram, showing all the forces actingon the box. (b) How would the diagram change if the boxwere sliding down the plane? (c) How would it change ifthe box were sliding up the plane after an initial shove?
(II) Figure 4–53 shows a block (mass ma) on a smooth hori- zontal surface, connected by a thin cord that passes over a pulley to a second block (mB), which hangs vertically. (a) Draw a free-body diagram for each block, showing the force of gravity on each, the force (tension) exerted by the cord, and any normal force. (b) Apply Newton's second law to find formulas for the acceleration of the system and for the tension in the cord. Ignore friction and the masses of the pulley and cord. FIGURE 4–53 Problems 32 and 33. mB Mass ma rests on a smooth horizontal surface; mâ hangs vertically.
Matt, in the foreground of Fig. 4–39, is able to move thelarge truck because(a) he is stronger than the truck.(b) he is heavier in some respects than the truck.(c) he exerts a greater force on the truck than the truckexerts back on him.(d) the ground exerts a greater friction force on Matt thanit does on the truck.(e) the truck offers no resistance because its brakes are off
(I) Draw the free-body diagram for a basketball player (a) just before leav- ing the ground on a jump, and (b) while in the air. See Fig. 4-46. TAK SPRS FIGURE 4-46 Problem 21.
(II) One 3.2-kg paint bucket is hanging by a massless cord from another 3.2-kg paint bucket, also hanging by a mass- less cord, as shown in Fig. 4–49. (a) If the buckets are at rest, what is the tension in each cord? (b) If the two buckets are pulled upward with an acceleration of 1.25 m/s² by the upper cord, calculate the tension in each cord. FIGURE 4–49 Problem 25.
(i) If a fly collides with the windshield of a fast-moving bus, which experiences an impact force with a larger magnitude? (a) The fly. (b) The bus. (c) The same force is experienced by both. (ii) Which experiences the greater acceleration? (a) The fly. (b) The bus. (c) The same acceleration is experienced by both.
An 18-kg child is riding in a child-restraint chair, securely fastened to the seat of a car (Fig. 4–77). Assume the car has speed 45 km/h when it hits a tree and is brought to rest in 0.20 s. Assuming constant deceleration during the colli- sion, estimate the net horizontal force F that the straps of the restraint chair exert on the child FIGURE 4–77 to hold her in the chair. Problem 97.