Physics for Scientists and Engineers: Foundations and Connections
1st Edition
ISBN: 9781133939146
Author: Katz, Debora M.
Publisher: Cengage Learning
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Chapter 14, Problem 21PQ
To determine
The torque exerted by the dumbbell around the shoulder.
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When you bend over, a series of large muscles, the erector spinae, pull on your spine to hold you up. The following figure shows a simplified model of the spine as a rod of length L that pivots at its lower end. In this model, the center of gravity of the 270 N270 N weight of the upper torso is at the center of the spine. The 140 N140 N weight of the head and arms acts at the top of the spine. The erector spinae muscles are modeled as a single muscle that acts at a 1212-degree angle to the spine. Suppose the person in the figure bends over to an angle of 3030 degrees from horizontal.
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The 3.0-m-long, 100 kg rigid beam of FIGURE EX12.31 is
supported at each end. An 80 kg student stands 2.0 m from
support 1. How much upward force does each support exert on
the beam?
FIGURE EX12.31
Support 1
2.0 m
3.0 m
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The fishing pole in Figure P8.3 makes an angle of 20.0°
with the horizontal. What is the magnitude of the torque exerted
by the fish about an axis perpendicular to the page and pass-
ing through the angler's hand if the fish pulls on the fishing
line with a force F = 1.00 × 10² N at an angle 37.0° below the
horizontal? The force is applied at a point 2.00 m from the
angler's hands.
120.0°
87.0°
-2.00 m-
120.0°
100 N
Figure P8.3
Chapter 14 Solutions
Physics for Scientists and Engineers: Foundations and Connections
Ch. 14.1 - A rubber duck floats in a bathtub. Imagine moving...Ch. 14.1 - Prob. 14.2CECh. 14.2 - CASE STUDY Hanging a Plane from a Single Point In...Ch. 14.2 - Prob. 14.4CECh. 14.4 - Imagine two vertical rods initially of equal...Ch. 14 - What Is Static Equilibrium? Problems 13 are...Ch. 14 - Prob. 2PQCh. 14 - Two identical balls are attached to a...Ch. 14 - While working on homework together, your friend...Ch. 14 - Consider the sketch of a portion of a...
Ch. 14 - Prob. 6PQCh. 14 - Prob. 7PQCh. 14 - Prob. 8PQCh. 14 - The keystone of an arch is the stone at the top...Ch. 14 - Prob. 10PQCh. 14 - Stand straight and comfortably with your feet...Ch. 14 - Prob. 12PQCh. 14 - Prob. 13PQCh. 14 - Prob. 14PQCh. 14 - Prob. 15PQCh. 14 - Prob. 16PQCh. 14 - Prob. 17PQCh. 14 - Prob. 18PQCh. 14 - Prob. 19PQCh. 14 - Prob. 20PQCh. 14 - Prob. 21PQCh. 14 - The inner planets of our solar system are...Ch. 14 - Two Boy Scouts, Bobby and Jimmy, are carrying a...Ch. 14 - Prob. 24PQCh. 14 - A painter of mass 87.8 kg is 1.45 m from the top...Ch. 14 - Consider the situation in Problem 25. Tests have...Ch. 14 - Children playing pirates have suspended a uniform...Ch. 14 - Prob. 28PQCh. 14 - Prob. 29PQCh. 14 - A 5.45-N beam of uniform density is 1.60 m long....Ch. 14 - A wooden door 2.1 m high and 0.90 m wide is hung...Ch. 14 - A 215-kg robotic arm at an assembly plant is...Ch. 14 - Problems 33 and 34 are paired. One end of a...Ch. 14 - For the uniform beam in Problem 33, find the...Ch. 14 - Prob. 35PQCh. 14 - A square plate with sides of length 4.0 m can...Ch. 14 - Prob. 37PQCh. 14 - At a museum, a 1300-kg model aircraft is hung from...Ch. 14 - A uniform wire (Y = 2.0 1011 N/m2) is subjected...Ch. 14 - A brass wire and a steel wire, both of the same...Ch. 14 - In Example 14.3, we found that one of the steel...Ch. 14 - A carbon nanotube is a nanometer-scale cylindrical...Ch. 14 - A nanotube with a Youngs modulus of 1.000 1012 Pa...Ch. 14 - Consider a nanotube with a Youngs modulus of 2.130...Ch. 14 - Prob. 45PQCh. 14 - Use the graph in Figure P14.46 to list the three...Ch. 14 - Prob. 47PQCh. 14 - A company is testing a new material made of...Ch. 14 - Prob. 49PQCh. 14 - Prob. 50PQCh. 14 - Prob. 51PQCh. 14 - Prob. 52PQCh. 14 - Prob. 53PQCh. 14 - Prob. 54PQCh. 14 - Prob. 55PQCh. 14 - Prob. 56PQCh. 14 - A copper rod with length 1.4 m and cross-sectional...Ch. 14 - Prob. 58PQCh. 14 - Prob. 59PQCh. 14 - Bruce Lee was famous for breaking concrete blocks...Ch. 14 - Prob. 61PQCh. 14 - Prob. 62PQCh. 14 - Prob. 63PQCh. 14 - A One end of a metal rod of weight Fg and length L...Ch. 14 - Prob. 65PQCh. 14 - A steel cable 2.00 m in length and with...Ch. 14 - Prob. 67PQCh. 14 - Prob. 68PQCh. 14 - Prob. 69PQCh. 14 - Prob. 70PQCh. 14 - Prob. 71PQCh. 14 - Prob. 72PQCh. 14 - Prob. 73PQCh. 14 - We know from studying friction forces that static...Ch. 14 - Ruby, with mass 55.0 kg, is trying to reach a box...Ch. 14 - An object is being weighed using an unequal-arm...Ch. 14 - Prob. 77PQCh. 14 - A massless, horizontal beam of length L and a...Ch. 14 - A rod of length 4.00 m with negligible mass is...Ch. 14 - A rod of length 4.00 m with negligible mass is...Ch. 14 - A horizontal, rigid bar of negligible weight is...Ch. 14 - Prob. 82PQCh. 14 - Prob. 83PQCh. 14 - Prob. 84PQCh. 14 - Prob. 85PQ
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- The fishing pole in Figure P10.22 makes an angle of 20.0 with the horizontal. What is the torque exerted by the fish about an axis perpendicular to the page and passing through the anglers hand if the fish pulls on the fishing line with a force F=100N at an angle 37.0 below the horizontal? The force is applied at a point 2.00 m from the anglers hands. Figure P10.22arrow_forward(a) When opening a door, you push on it perpendicularly with a force of 55.0 N at a distance of 0.850m from the hinges. What torque are you exerting relative to the hinges? (b) Does it matter if you push at the same height as the hinges?arrow_forwardFind the net torque on the wheel in Figure P10.23 about the axle through O, taking a = 10.0 cm and b = 25.0 cm. Figure P10.23arrow_forward
- (a) When opening a door, you push on it perpendicularly with a force of 55.0 N at a distance of 0.850 m from the hinges. What torque are you exerting relative to the hinges? (b) Does it matter if you push at the same height as the hinges? There is only one pair of hinges.arrow_forwardRuby, with mass 55.0 kg, is trying to reach a box on a high shelf by standing on her tiptoes. In this position, half her weight is supported by the normal force exerted by the floor on the toes of each foot as shown in Figure P14.75A. This situation can be modeled mechanically by representing the force on Rubys Achilles tendon with FA and the force on her tibia as FT as shown in Figure P14.75B. What is the value of the angle and the magnitudes of the forces FA and FT? FIGURE P14.75arrow_forwardWhy is the following situation impossible? A uniform beam of mass mk = 3.00 kg and length = 1.00 m supports blocks with masses m1 = 5.00 kg and m2 = 15.0 kg at two positions as shown in Figure P12.2. The beam rests on two triangular blocks, with point P a distance d = 0.300 m to the right of the center of gravity of the beam. The position of the object of mass m2 is adjusted along the length of the beam until the normal force on the beam at O is zero. Figure P12.2arrow_forward
- A square plate with sides 2.0 m in length can rotatearound an axle passingthrough its center of mass(CM) and perpendicular toits surface (Fig. P12.53). There are four forces acting on the plate at differentpoints. The rotational inertia of the plate is 24 kg m2. Use the values given in the figure to answer the following questions. a. Whatis the net torque acting onthe plate? b. What is theangular acceleration of the plate? FIGURE P12.53 Problems 53 and 54.arrow_forwardA square plate with sides of length 4.0 m can rotate about an axle passing through its center of mass and perpendicular to the plate as shown in Figure P14.36. There are four forces acting on the plate at different points. The rotational inertia of the plate is 24 kgm2. Is the plate in equilibrium? FIGURE P14.36arrow_forwardA disk with a radius of 4.5 m has a 100-N force applied to its outer edge at two different angles (Fig. P12.55). The disk has arotational inertia of 165 kg m2. a. What is the magnitude of the torque applied to the disk incase 1? b. What is the magnitude of the torque applied to the disk incase 2? c. Assuming the force on the disk is constant in each case,what is the magnitude of the angular acceleration applied tothe disk in each case? d. Which case is a more effective way of spinning the disk?Describe which quantity you are using to determine effectiveness and why you chose that quantity. FIGURE P12.55arrow_forward
- The fishing pole in Figure P10.28 makes an angle of 20.0 with the horizontal. What is the torque exerted by the fish about an axis perpendicular to the page and passing through the anglers hand if the fish pulls on the fishing line with a force F = 100 N at an angle 37.0 below the horizontal? The force is applied at a point 2.00 in from the anglers hands.arrow_forwardA massless, horizontal beam of length L and a massless rope support a sign of mass m (Fig. P14.78). a. What is the tension in the rope? b. In terms of m, g, d, L, and , what are the components of the force exerted by the beam on the wall? FIGURE P14.78arrow_forward(a) Give an example in which the net force acting on an object is zero, yet the net torque is nonzero, (b) Give an example in which the net torque acting on an object is zero, yet the net force is nonzero.arrow_forward
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