ASVAB Mechanical Comprehension Practice Test 253046 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.70
Score	0%	54%

Review

Friction resists movement in a direction __________ to the movement.

81% Answer Correctly

	normal
	opposite
	parallel
	perpendicular

Solution

Friction resists movement. Kinetic (also called sliding or dynamic) friction resists movement in a direction opposite to the movement. Because it opposes movement, kinetic friction will eventually bring an object to a stop. An example is a rock that's sliding across ice.

2 If the radius of the axle is 3 and the radius of the wheel is 6, what is the mechanical advantage of this wheel and axle configuration?

36% Answer Correctly

	-3
	3
	6
	1

Solution

The mechanical advantage of a wheel and axle lies in the difference in radius between the inner (axle) wheel and the outer wheel. But, this mechanical advantage is only realized when the input effort and load are applied to different wheels. Applying both input effort and load to the same wheel results in a mechanical advantage of 1.

Force of friction due to kinetic friction is __________ the force of friction due to static friction.

40% Answer Correctly

	the same as
	opposite
	lower than
	higher than

Solution

The formula for force of friction (F_f) is the same whether kinetic or static friction applies: F_{f =}μF_N. To distinguish between kinetic and static friction, μ_k and μ_s are often used in place of μ.

What type of load is sudden and for a relatively short duration?

69% Answer Correctly

	concentrated load
	non-uniformly distributed load
	dynamic load
	impact load

Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

5 What is the power output of a 3 hp engine that's 70% efficient?

40% Answer Correctly

	577.5 \( \frac{ft⋅lb}{s} \)
	2310 \( \frac{ft⋅lb}{s} \)
	4620 \( \frac{ft⋅lb}{s} \)
	1155 \( \frac{ft⋅lb}{s} \)

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 3 hp x 550 \( \frac{ft⋅lb}{s} \) = 1650 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{70 \times 1650 \frac{ft⋅lb}{s}}{100} \) \( = \frac{115500 \frac{ft⋅lb}{s}}{100} \) = 1155 \( \frac{ft⋅lb}{s} \)