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Sample Practice Test Questions
The spark plugs fire a few extra degrees before top dead center when the engine is running faster. In this case the engine's timing is:
advanced
Ignition timing defines the point in time at the end of the compression stroke that the spark plug fires. Measured in number of degrees before top dead center (BTDC), the exact point that the spark plugs initiate combustion varies depending on the speed of the engine. The timing is advanced (the spark plugs fire a few more degrees BTDC) when the engine is running faster and retarded when it's running slower.
If the radius of the axle is 5 and the radius of the wheel is 6, what is the mechanical advantage of this wheel and axle configuration?
The mechanical advantage of a wheel and axle is the input radius divided by the output radius:
MA = \( \frac{r_i}{r_o} \)
In this case, the input radius (where the effort force is being applied) is 6 and the output radius (where the resistance is being applied) is 5 for a mechanical advantage of \( \frac{6}{5} \) = 1.2
If the base of this triangle is 6 and the height is 7, what is the area?
The area of a triangle is equal to ½ base x height:
a = ½bh
a = ½ x 6 x 7 = \( \frac{42}{2} \) = 21
The combustion chamber is enclosed by the:
cylinder head
Cylinders act as a guide for the pistons that translate the heat energy of combustion into the mechanical energy necessary to move a vehicle. Piston rings seal the piston to the cylinder to contain combustion gases and also regulate the oil distribution between the piston and cylinder wall. A cylinder head closes in the top of the cylinder forming the combustion chamber which is sealed by a head gasket (head). The head provides space for air and fuel intake valves, exhaust valves, and mounts for spark plugs and fuel injectors.
The formula for the area of a circle is which of the following?
a = π r2
The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)2 : a = π r2.
Solve for a:
a2 + 6a - 13 = -a + 5
The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:
a2 + 6a - 13 = -a + 5
a2 + 6a - 13 - 5 = -a
a2 + 6a + a - 18 = 0
a2 + 7a - 18 = 0
Next, factor the quadratic equation:
a2 + 7a - 18 = 0
(a - 2)(a + 9) = 0
For this expression to be true, the left side of the expression must equal zero. Therefore, either (a - 2) or (a + 9) must equal zero:
If (a - 2) = 0, a must equal 2
If (a + 9) = 0, a must equal -9
So the solution is that a = 2 or -9
An overcooled engine:
is less efficient
An overcooled engine is less efficient. During the power stroke, combustion heat pushes down the piston. If too much of this heat is lost to the cooling system, the fuel might not combust completely and contaminate the engine's lubricating oil diminishing its lubricating ability. Incomplete combustion of fuel also negatively affects the engine's fuel efficiency and power output.
A diode to an electronic circuit is like a _______________ to a city?
one-way street
A diode allows current to pass easily in one direction and blocks current in the other direction.