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# (A) \VJ FIGURE 4-39 PROBLEM 27

By Laura Phillips,2014-07-08 10:11
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(A) DRAW THE FREE-BODY DIAGRAM SHOWING ALL FORCES ACTING ON THE MOWER. CALCULATE ( B ) THE HORIZONTAL RETARDING FORCE ON THE MOWER, THEN (C) THE NORMAL FORCE ...

Mayfield physics force problems #2

1.The two forces F and F shown in Fig. below and b (looking down) act on a 27.0-kg object on a frictionless tabletop. If l2

F = 10.2 N and F = 16.0 N, 3 find the net force on the object and its acceleration for each situation, (a) and (b). l2

2.A person pushes a 14.5-kg lawn mower at constant speed with a force of 88.0 N directed along the handle, which is at an angle of 45.0? to the horizontal. (a) Draw the free-body diagram showing all forces acting on the mower. Calculate ( b ) the horizontal retarding force on the mower, then (c) the normal force exerted vertically upward on the mower by the ground, and (d) the force the person must exert on the lawn mower to accelerate it from rest to 1.5 m/s in 2.5 seconds ( assuming the same retarding force ).

3.At the instant a race began, a 65-kg sprinter was found to exert a force of 800 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 0.38 s, with what speed did the sprinter leave the starting block?

4. One 3.0-kg paint bucket is hanging by a mass less cord from another 3.0-kg paint bucket, also hand, by a mass less cord, as shown in Fig. 4-41. (a) If buckets are at rest, what is the tension in each cord (b) If the two buckets are pulled upward with an acceleration of 1.60 m/s2 by the upper cord, calculate the tension in each cord.

Mayfield physics force problems #2

2-kg helicopter accelerates upward 0.60 m/s while lifting a 1200-kg car. (a) What is lifting force exerted by the 5. A 6500

air on the rotors? (b) Is the tension in the cable (ignore its mass) that connects the car to the helicopter?

6. A window washer pulls herself upward using! Bucket-pulley apparatus shown in Fig (a) how hard must she pull downward to raise herself at constant speed? (b) If she increases this force 10 percent, what will her acceleration be? The mass of the person plus the bucket is 65 kg.

7. A train locomotive is pulling two cars of the same mass behind it. Show that the tension in the coupling between the locomotive and the first car is twice that between the first car and the second car, for any nonzero acceleration of the train.

8. A pair of fuzzy dice is hanging by a string from your rearview mirror while your accelerating from a stoplight to 20 m/s (in 5.0 secs) What angle θ does the string make with the vertical?

Mayfield physics force problems #2

9. Three blocks on a frictionless horizontal required to move the crate at a steady speed across the face are in contact with each other, as shown in floor? What horizontal force is required if. μ is zero? A force F is applied to block 1 (mass m) k1

10. The two masses shown are each initially 1.80 m above the ground and the mass less frictionless pulley is 4.8 m above the ground maximum height does the lighter object reach after the system is released? Hint: first determine the acceleration of the highest mass and then its velocity at the moment the heavier one hits the ground. This is its launch speed.

11. Suppose the cord in Example 4-10 and Fig. 4-22 is a heavy rope of mass 1.0 kg. Calculate the acceleration of each box and the tension at each end of the cord, using the free-body diagrams shown in Fig. 4-46. Assume the cord doesn't sag.

Mayfield physics force problems #2

12. If the coefficient of kinetic friction between a 35-kg crate and the floor is 0.30, what horizontal force is required to move the crate at a steady speed across the floor? What horizontal force if μ is zero? k

a force of 40.0 N is required to start a 5.0-kg box- moving across a horizontal concrete floor

(a) Draw a free-body diagram for each block. De. (a) What is the coefficient of static friction between the box and

the floor? 2(b) If the 40.0-N force continues, the box accelerates a 0.70 m/s what is the coefficient of kinetic friction?

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