COMBINATION PRACTICE TEST - SD CDL
11.
What is a tractor jackknife?
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When a drive-wheel skid lets the trailer push the towing vehicle sideways.
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When the wheels of a trailer lock up, and the trailer swings around.
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When the rear wheels of a trailer lock up, and the tractor swings around.
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None of the above.
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12.
The tractor protection valve:
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keeps air in the tractor brake system should the trailer break away or develop a bad leak.
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controls the emergency brakes on combination vehicles.
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works the trailer brakes.
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supplies air to the trailer air tanks.
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13.
Tests have shown that trucks with a high center of gravity are more likely to tip over, therefore you should:
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distribute the cargo as low as possible.
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put the lightest parts of the cargo under the heaviest parts.
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distribute the cargo so the majority of the weight is on the steering axle.
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All of the above.
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14.
The trailer hand valve should be used only:
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only in combination with the foot brake.
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when the trailer is fully loaded.
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to test the trailer brakes.
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in driving to prevent skids.
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15.
When backing a trailer, you should:
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pull-up frequently to reposition the vehicle.
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not back up in a straight line.
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turn the steering wheel toward the direction you want to go.
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avoid braking.
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16.
When should you use the hand valve to park a combination vehicle?
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To park at loading docks.
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Never.
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When parking downhill.
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Always.
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17.
Empty trucks have the best braking. True or False?
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True.
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It depends on the truck.
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It depends on the cargo.
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False.
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18.
When you are uncoupling a loaded trailer, lower the landing gear until:
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makes contact with the ground, and leave the trailer off the fifth wheel.
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the tractor frame is under the trailer.
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the pressure in the system is above 55 psi.
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it makes firm contact with the ground.
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19.
When you have to back, you should always try to back toward the driver's side. Why?
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You can watch the front of your vehicle by looking out the side window.
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Backing toward the left side is more dangerous.
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You can see better and watch the rear of your vehicle by looking out the side window.
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All of the above.
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20.
Which of the following is NOT a step in backing up with a trailer?
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Looking at your line of travel before you begin
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Checking the outside mirrors on both sides frequently
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Backing slowly
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Backing quickly when the path is straight
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