ASVAB Mechanical Comprehension Practice Test 946288 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.51
Score	0%	50%

Review

The mechanical advantage of a block and tackle is equal to which of the following?

69% Answer Correctly

	the number of pulleys
	the number of loads
	the number of connecting ropes
	the number of input forces

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

2 What is the power output of a 8 hp engine that's 70% efficient?

39% Answer Correctly

	560 \( \frac{ft⋅lb}{s} \)
	0 \( \frac{ft⋅lb}{s} \)
	3080 \( \frac{ft⋅lb}{s} \)
	770 \( \frac{ft⋅lb}{s} \)

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 8 hp x 550 \( \frac{ft⋅lb}{s} \) = 4400 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{70 \times 4400 \frac{ft⋅lb}{s}}{100} \) \( = \frac{308000 \frac{ft⋅lb}{s}}{100} \) = 3080 \( \frac{ft⋅lb}{s} \)

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

	speed or power
	force or distance
	force or speed
	power or distance

Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

Which of the following is not a type of structural load?

49% Answer Correctly

	dead load
	live load
	occupancy load
	wind load

Solution

Dead load is the weight of the building and materials, live load is additional weight due to occupancy or use, snow load is the weight of accumulated snow on a structure and wind load is the force of wind pressures against structure surfaces.

Which of the following statements about this pulley configuration is false?

48% Answer Correctly

	Mechanical advantage is the number of ropes that support the resistance
	This is a block and tackle pulley configuration
	Changes the direction of and multiplies the effort force
	Only multiplies the effort force

Solution

A block and tackle is a combination of one or more fixed pulleys and one or more movable pulleys where the fixed pulleys change the direction of the effort force and the movable pulleys multiply it. The mechanical advantage is equal to the number of times the effort force changes direction and can be increased by adding more pulley wheels to the system. An easy way to find the mechanical advantage of a block and tackle pulley system is to count the number of ropes that support the resistance.