8–55. A blade on a straight–blade dozer must  have  what  type  of  accessory before it can be used as a push dozer? 1. A cutting edge 2. A hard facing 3. A  reinforced  block 4. A rubber bumper 8-56. An operator of a dozer should always wear   a seat belt when dozing. 1. True 2. False Learning  Objective: Recognize the  principles  and  components of  rollers. 8-57. What term is used to describe the process  of  compressing  loose  soil into a solid mass? 1. Crushing 2. Compaction 3. Pulverizing 4. Condensing 8-58. In  roller  operations,  what  does the acronym vpm mean? 1. Vibration  per  mile 2. Vibration  pounding  minutes 3. Vibrations  per  minute 4. Vibrations pulsate moment 8-59. Vibratory  rollers  achieve compaction  through  which of  the  following  factors? 1. Weight 2. Impact  forces 3. Vibration  response 4. All of the above 8-60. The impact forces placed on the soil during compaction are generated by what action of the roller? 1. The weight of the roller 2. The  vibration  of  the  drum 3. The  kneading  effort  of  the tires 4. The speed of the roller 8-61. A sheepsfoot drum is used for compacting  heavy  lifts  of  what thickness  range? 1. 3  to  4  inches 2. 6 to 12 inches 3. 12 to 24 inches 4. 24 to 36 inches 8–62. A smooth drum roller is capable of compacting  lifts  of  what  thickness range? 1. 4  to  8  inches 2. 8 to 16 inches 3. 16 to 32 inches 4. 32 to 64 inches 8-63. What  type  of  compaction  effort is  generated  by  a  pneumatic-tired roller? 1. Vibration 2. Pounding 3. Kneading  effect 4. Shaking 8-64. The air pressure in the tires of a  pneumatic-tired  roller  should be set at what psi to compact a granular  subbase? 1. 40 psi 2. 60  psi 3. 80  psi 4. 100  psi 8-65. What type of roller may fail to compact  areas   narrower  than  the roll and does NOT compact deeply in proportion  to  the  roller  weight? 1. Sheepsfoot 2. Steel  wheel 3. Pneumatic  tired 4. Smooth  drum 61