Physics for Scientists and Engineers, 6e Chapter 12 - Static Equilibrium and Elasticity

Consider the object subject to the two forces in the figure below Consider the object subject to the two forces in the figure below. Choose the correct statement with regard to this situation. The object is in force equilibrium but not torque equilibrium. The object is in torque equilibrium but not force equilibrium. The object is in both force and torque equilibrium. The object is in neither force nor torque equilibrium. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

The unbalanced torques due to the forces in Figure 12 The unbalanced torques due to the forces in Figure 12.2 cause an angular acceleration even though the linear acceleration is zero.

Consider the object subject to the three forces in the figure below Consider the object subject to the three forces in the figure below. Choose the correct statement with regard to this situation. The object is in force equilibrium but not torque equilibrium. The object is in torque equilibrium but not force equilibrium. The object is in both force and torque equilibrium. The object is in neither force nor torque equilibrium 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

Notice that the lines of action of all the forces in Figure 12 Notice that the lines of action of all the forces in Figure 12.3 intersect at a common point. Thus, the net torque about this point is zero. This zero value of the net torque is independent of the values of the forces. Because no force has a downward component, there is a net force and the object is not in force equilibrium.

impossible to determine A meter stick is supported on a fulcrum at the 25-cm mark. A 0.50-kg object is hung from the zero end of the meter stick, and the stick is balanced horizontally. The mass of the meter stick is 0.25 kg 0.50 kg 0.75 kg 1.0 kg 2.0 kg impossible to determine 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

Both the object and the center of gravity of the meter stick are 25 cm from the pivot point. Thus, the meter stick and the object must have the same mass if the system is balanced.

A block of iron is sliding across a horizontal floor A block of iron is sliding across a horizontal floor. The friction force between the block and the floor causes the block to deform. To describe the relationship between stress and strain for the block, you would use Young's modulus shear modulus bulk modulus none of these 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

The friction force on the block as it slides along the surface is parallel to the lower surface and will cause the block to undergo a shear deformation.

A trapeze artist swings through a circular arc A trapeze artist swings through a circular arc. At the bottom of the swing, the wires supporting the trapeze are longer than when the trapeze artist simply hangs from the trapeze, due to the increased tension in them. To describe the relationship between stress and strain for the wires, you would use Young's modulus shear modulus bulk modulus none of these 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

The stretching of the wire due to the increased tension is described by Young’s modulus

A spacecraft carries a steel sphere to a planet on which atmospheric pressure is much higher than on the Earth. The higher pressure causes the radius of the sphere to decrease. To describe the relationship between stress and strain for the sphere, you would use Young's modulus shear modulus bulk modulus none of these 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

The pressure of the atmosphere results in a force of uniform magnitude perpendicular at all points on the surface of the sphere.