ASVAB Mechanical Comprehension Practice Test 681884 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.36
Score	0%	67%

Review

1 If this lever is in equilibrium with an effort force of 11.25 ft. lb. at the blue arrow and a resistance force of 9 ft. lb. at the green box, what is its mechanical advantage?

48% Answer Correctly

	2.8
	0.8
	0.27
	0.4

Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{9 ft.}{11.25 ft.} \) = 0.8

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.8 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.

The steering wheel of a car is an example of which type of simple machine?

89% Answer Correctly

	first-class lever
	block and tackle
	wheel and axle
	fixed pulley

Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

3 What is the power output of a 9 hp engine that's 35% efficient?

40% Answer Correctly

	1732.5 \( \frac{ft⋅lb}{s} \)
	5197.5 \( \frac{ft⋅lb}{s} \)
	433.1 \( \frac{ft⋅lb}{s} \)
	866.3 \( \frac{ft⋅lb}{s} \)

Solution

\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), P_i becomes 9 hp x 550 \( \frac{ft⋅lb}{s} \) = 4950 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{35 \times 4950 \frac{ft⋅lb}{s}}{100} \) \( = \frac{173250 \frac{ft⋅lb}{s}}{100} \) = 1732.5 \( \frac{ft⋅lb}{s} \)

When all forces acting on a system cancel each other out, this is called:

81% Answer Correctly

	rest
	potential energy
	stasis
	equilibrium

Solution

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.

Which of the following is not a type of bridge?

74% Answer Correctly

	block
	arch
	cable
	truss

Solution

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.