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Sample Practice Test Questions
The gear ratio (Vr) of a gear train is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:
Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)
In this problem, we have only two gears so the equation becomes:Vr = \( \frac{N_1}{N_2} \) = \( \frac{32}{4} \) = 8
If all of a roofing company's 6 workers are required to staff 3 roofing crews, how many workers need to be added during the busy season in order to send 7 complete crews out on jobs?
In order to find how many additional workers are needed to staff the extra crews you first need to calculate how many workers are on a crew. There are 6 workers at the company now and that's enough to staff 3 crews so there are \( \frac{6}{3} \) = 2 workers on a crew. 7 crews are needed for the busy season which, at 2 workers per crew, means that the roofing company will need 7 x 2 = 14 total workers to staff the crews during the busy season. The company already employs 6 workers so they need to add 14 - 6 = 8 new staff for the busy season.
The standard unit of energy is the:
Joule
The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).
If the force applied at the blue arrow over 5 ft. moves the green box 2.5 ft., what is the mechanical advantage of this lever?
Mechanical advantage (MA) can be calculated knowing only the distance the effort (blue arrow) moves and the distance the resistance (green box) moves. The equation is:
MA = \( \frac{E_d}{R_d} \)
where Ed is the effort distance and Rd is the resistance distance. For this problem, the equation becomes:
MA = \( \frac{5 ft.}{2.5 ft.} \) = 2
You might be wondering how having an effort distance of 2 times the resistance distance is an advantage. Remember the principle of moments. For a lever in equilibrium the effort torque equals the resistance torque. Because torque is force x distance, if the effort distance is 2 times the resistance distance, the effort force must be \( \frac{1}{2} \) the resistance force. You're trading moving 2 times the distance for only having to use \( \frac{1}{2} \) the force.
Specific gravity is a comparison of the density of an object with the density of:
water
Specific gravity is the ratio of the density of equal volumes of a substance and water and is measured by a hyrdometer.
Gases from combustion are pushed out through the exhaust valve as the piston travels up the cylinder to top dead center. This describes which engine stroke?
exhaust
During the exhaust stroke, just before the piston reaches bottom dead center the exhaust valve opens. The resulting gases from combustion are then pushed out through the exhaust valve as the piston travels up the cylinder to top dead center, completing stroke four of the four-stroke piston cycle.