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Sample Practice Test Questions
Which of the following statements about drag is false?
slower objects experience more drag than faster objects
Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.
The radius of the axle is 3, the radius of the wheel is 4, and the blue box weighs 35 lbs. What is the effort force necessary to balance the load?
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 4 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of \( \frac{4}{3} \) = 1.33
MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{35 lbs.}{1.33} \) = 26.32 lbs.
Which of the following is the primary difference between a comet and an asteroid?
comets have an atmosphere
A comet is a loose collection of ice, dust, and small rocky particles that, in contrast to an asteroid, has an extended atmosphere surrounding the center. When passing close to the Sun, this atmosphere warms and begins to release gases forming a visible coma or tail.
Inductance is a factor in which of the following?
an AC circuit
Inductance is a property of an AC circuit (or a component in an AC circuit) that quantifies resistance to changes in current. The current in an AC circuit is continuously changing and inductive reactance (the opposition to change) depends both on the inductance of the circuit or component and the rate at which the current is changing.
When cutting hard metals with a hacksaw you should choose a blade with __________ teeth per inch (TPI).
high
Blades with more and smaller teeth (high TPI) cut harder metals more effectively while blades with fewer and larger teeth (low TPI) cut softer metals more effectively.
Hydraulics is the transmission of force through the use of which of the following?
liquids
Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).
The conversion of alternating current (AC) into direct current (DC) is called:
rectification
A diode allows current to pass easily in one direction and blocks current in the other direction. Diodes are commonly used for rectification which is the conversion of alternating current (AC) into direct current (DC). Because a diode only allows current flow in one direction, it will pass either the upper or lower half of AC waves (half-wave rectification) creating pulsating DC. Multiple diodes can be connected together to utilize both halves of the AC signal in full-wave rectification.