ASVAB Auto and Shop Practice Test 2024 [with Explanation PDF]

The differential and driveshaft are the big moving parts at the rear of a rear-wheel-drive car with the engine in front.

Either the spark plug is not working right or there is a problem with the incoming fuel-air mix.  

Air pressure inside the tire pushes evenly against the entire inside of the tire, allowing it to hold its shape and to respond to unevenness in
the road. Low tire pressure reduces efficiency, and engine power is converted into heat, which warms the tire.  

Breaker points send quick jolts of electricity to the coil, which acts as a transformer to raise the voltage enough to spark a spark plug. The gap
must be adjusted during a tune-up, and should be inspected whenever the engine runs rough.  

Front-wheel-drive mechanisms are complicated because they both drive and steer.  

Intake: The piston moves down, creating a partial vacuum that draws air (and sometimes fuel) into the cylinder. Compression: The piston moves up with both valves closed, compressing the airfuel mixture. Power: The fuel explodes, creating heat and kinetic energy, pushing the piston down. Exhaust: The piston moves up, pushing burned gases from the cylinder through the exhaust valve. Choice A is tempting, but a four-cycle engine has no “rest” cycle. The cylinder is always working.  

The fuel system must deliver enough fuel for combustion inside the engine. Choice D, the engine control module, is the second-best answer.
Although it could cause the problem, the fuel system is the first thing to check  

Manual transmissions usually have one “direct-drive” gear, where the input speed is the same as the output speed. The drive shaft rotates
along with the transmission’s output shaft. Choice D is incorrect because the clutch moves at the same speed as the engine.  

Because the pistons in the wheel cylinders are the only movable objects in the system, when you move the master cylinder, hydraulic fluid forces the pistons in the wheel cylinders to move.  

The starter relay is a big switch located between the battery and the starter motor. Starter motors demand a huge current, which would require an expensive and clumsy cable from the battery to the ignition switch and the starter motor. Instead, the ignition switch activates the starter relay, which temporarily connects the battery to the starter motor.  

After the power stroke, there is nothing left to burn inside the cylinder. The exhaust stroke clears the cylinder out through the exhaust valve, making room for a fresh fuel-air mixture. The engine will not run at all unless the exhaust valve opens.  

The differential has reduction gears so that the engine can turn fast enough to make power. A 3- to-1 ratio means that 3 turns of the driveshaft produce 1 turn of the wheels. Why are the other answers incorrect? Choice A: The engine would run too slowly to make power. Choice B: Cars do not have a jack shaft. Choice C: The ring gear in a differential cannot be disengaged 

A blade that is as wide as the screw head will put maximum turning power on the screw.  

Arc-joint pliers, commonly called Channel Locks, can adjust to grip a wide variety of objects  

Plywood splinters easily, and each small tooth takes a smaller “bite,” reducing splintering. Why are the other answers incorrect? Choice A: Big teeth cause more splintering. Choice B: A plywood blade is fine for particle board. Choice C is dead wrong. In saw blades, sharper is better!  

Choice D is tempting, but a claw hammer can drive some wood chisels without damage.  

Bar clamps are also handy for holding parts for sawing or drilling, but not for the other three purposes listed.  

Impact equals mass times velocity, so a more massive hammer makes more impact for any given hammer speed. Why are the other answers
incorrect? Choice A: Mass, not weight, determines the intensity of impact. Choice C: Size alone does not make the hammer more effective.
Choice D: A slower-moving hammer will be less effective at driving the chisel.  

Plywood is stronger than regular wood because the grain is crisscrossed, preventing splitting and reducing weakness at knots. Why are the
other answers incorrect? Choice A: Plywood may be weatherproof, but subfloors don’t face the weather. Choices B and C: Plywood may be
lighter and thinner, but that’s not as important as strength in a subfloor.  

An oxyacetylene cutting torch is made for cutting metal. Why are the other answers incorrect? All the saws mentioned are designed to cut wood.  

Tin snips act like big scissors to shear sheet metal.  

A pipe wrench fits loosely on the pipe; turning activates the grabbing action. The other tools all must be tightened before use.  

A sharp drill bit cuts faster, cooler, and with less pressure on the drill, but it makes the same amount of chips.  

Cold water will cause the nut to contract and grab tighter on the bolt. A frozen (rusted) nut can be loosened with heat, which causes it to expand, by pounding, which creates vibration, or by penetrating oil, which softens rust.  

A plumb line is vertical and a level line is horizontal, so the angle between them is square, or 90°.