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Sample Practice Test Questions
The advantage of using a third-class lever is that it increases:
the speed of the load
A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.
Silver and gold are among the most highly conductive elements. Why is copper used much more often as a conductor in electrical circuits?
all of these
All conductors have resistance and the amount of resistance varies with the element. But, resistance isn't the only consideration when choosing a conductor as the most highly conductive elements like silver and gold are also more expensive and more brittle than slightly less conductive elements like copper. A balance needs to be struck between the electrical qualities of a material and its cost and durability.
The primary difference between a standard level and a bullseye level is which of the following?
a bullseye level can measure across two dimensions
Levels utlize a fluid-filled tube containing a bubble that is centered when the surface is horizontal (level) or vertical (plumb) along the direction of the tube. While a standard level can measure along a single dimension, a bullseye level is circular and can indicate the levelness of a two dimensional plane.
You would measure the amount of current through a circuit with a(n):
ammeter
Current is the rate of flow of electrons per unit time and is measured in amperes (A). An ammeter is used to measure the electric current in a circuit.
The green box weighs 10 lbs. and a 35 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow. How far from the fulcrum would the green box need to be placed to balance the lever?
To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:
Rada = Rbdb
where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.Solving for da, our missing value, and plugging in our variables yields:
da = \( \frac{R_bd_b}{R_a} \) = \( \frac{35 lbs. \times 3 ft.}{10 lbs.} \) = \( \frac{105 ft⋅lb}{10 lbs.} \) = 10.5 ft.
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