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Sample Practice Test Questions
When all forces acting on a system cancel each other out, this is called:
equilibrium
When a system is stable or balanced (equilibrium) all forces acting on the system cancel each other out. In the case of torque, equilibrium means that the sum of the anticlockwise moments about a center of rotation equal the sum of the clockwise moments.
If A = 10 ft., B = 1 ft., C = 9 ft., the green box weighs 50 lbs. and the blue box weighs 60 lbs., what does the orange box have to weigh for this lever to balance?
fAdA = fBdB + fCdC
For this problem, this equation becomes:
50 lbs. x 10 ft. = 60 lbs. x 1 ft. + fC x 9 ft.
500 ft. lbs. = 60 ft. lbs. + fC x 9 ft.
fC = \( \frac{500 ft. lbs. - 60 ft. lbs.}{9 ft.} \) = \( \frac{440 ft. lbs.}{9 ft.} \) = 48.89 lbs.
This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:
Fede = Frdr
Plugging in the variables from this problem yields:
Fe x 14 ft. = 290 lbs. x 2 ft.
Fe = \( \frac{580 ft⋅lb}{14 ft.} \) = 41.4 lbs.
A box is resting on a smooth floor. Static friction is present:
when an attempt is made to move the box
For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).
Simplify (5a)(2ab) - (9a2)(3b).
To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.
(5a)(2ab) - (9a2)(3b)
(5 x 2)(a x a x b) - (9 x 3)(a2 x b)
(10)(a1+1 x b) - (27)(a2b)
10a2b - 27a2b
-17a2b
The firing order of the cylinders in an engine can be found by:
observing the order in which the intake valves open
The firing order of the cylinders in an engine is different than the cynlinder numbers and can be found by observing the order in which the intake valves open.
Which of the following is not a type of bridge?
block
The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.
In the water cycle, infiltration is most closely related to:
water table
The water then accumulates as runoff and eventually returns to bodies of water or is absorbed into the Earth (infiltration) and becomes part of the water table, an underground resevoir of fresh water.