Q 12 Static Equilibrium 1 A picture can

Q 12. Static Equilibrium

1. A picture can be hung on a wall in three different ways, as shown. The tension in the string is: 1. least in I 2. greatest in I 3. greatest in II 4. least in III 5. greatest in III

II is min. III is max. 1. least in I 2. greatest in I 3. greatest in II 4. least in III 5. greatest in III

2. A uniform plank XY is supported by two equal 120 -N forces at X and Y, as shown. The support at X is then moved to Z (half-way to the plank center). The supporting forces at Y and Z are then: : 1. FY = 240 N, FZ = 120 N 2. FY = 200 N, FZ = 40 N 3. FY = 40 N, FZ = 200 N 4. FY = 80 N, FZ = 160 N 5. FY = 160 N, FZ = 80 N

Using Y as pivot : ( points upward ) 1. FY = 240 N, FZ = 120 N 2. FY = 200 N, FZ = 40 N 3. FY = 40 N, FZ = 200 N 4. FY = 80 N, FZ = 160 N 5. FY = 160 N, FZ = 80 N

3. A uniform rod AB is 1. 2 m long and weighs 16 N. suspended by strings AC and BD as shown. A block P weighing 96 N is attached at E, 0. 30 m from A. magnitude of the tension force in the string BD is: 1. 8. 0 N 2. 24 N 3. 32 N 4. 48 N 5. 80 N It is The

1. 2 m T 0. 3 m 96 N Using A as pivot : 1. 8. 0 N 2. 24 N 3. 32 N 4. 48 N 5. 80 N

4. A 5. 0 m weightless strut, hinged to a wall, is used to support a 800 -N block as shown. The horizontal and vertical components of the force of the hinge on the strut are: 1. FH = 800 N, FY = 800 N 2. FH = 600 N, FY = 800 N 3. FH = 800 N, FY = 600 N 4. FH = 1200 N, FY = 800 N 5. FH = 0 , FY = 800 N

FY F 1. FH = 800 N, FY = 800 N 2. FH = 600 N, FY = 800 N 3. FH = 800 N, FY = 600 N 4. FH = 1200 N, FY = 800 N 5. FH = 0 , FH Using hinge as pivot : FY = 800 N

5. A window washer attempts to lean a ladder against a frictionless wall. He finds that the ladder slips on the ground when it is placed at an angle of less than 75° to the ground but remains in place when the angle is greater than 75°. The coefficient of static friction between the ladder and the ground: 1. is about 0. 13 2. is about 0. 27 3. is about 1. 3 4. depends on the mass of the ladder 5. depends on the length of the ladder

L Total force = 0 1. is about 0. 13 2. is about 0. 27 3. is about 1. 3 4. depends on the mass of the ladder 5. depends on the length of the ladder Choose pivot point to be contact point on ground: N = N when 75°

6. The uniform rod shown below is held in place by the rope and wall. dimensions. Suppose you know the weight of the rod and all Then you can solve a single equation for the force exerted by the rope, provided you write expressions for the torques about the point: : 1. 1 2. 2 3. 3 4. 4 5. 1, 2, or 3

T Unknown forces are rope tension T & F 2. Choosing pivot point at 2 gives equation for one unknown T. 1. 1 2. 2 3. 3 4. 4 5. 1, 2, or 3

7. Bridge and Truck: Movie When the truck moves to the right, the force(s) on 1. the left scale increases. 2. the right scale increases. 3. both scales remain the same.

Movie