ASVAB Mechanical Comprehension Practice Test 498258 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.55
Score	0%	51%

Review

Which of the following represents the force a surface exerts when an object presses against it?

48% Answer Correctly

	mass
	friction
	counter force
	normal force

Solution

Normal force (F_N) represents the force a surface exerts when an object presses against it.

2 What is the power output of a 4 hp engine that's 85% efficient?

40% Answer Correctly

	5610 \( \frac{ft⋅lb}{s} \)
	0 \( \frac{ft⋅lb}{s} \)
	1870 \( \frac{ft⋅lb}{s} \)
	467.5 \( \frac{ft⋅lb}{s} \)

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 4 hp x 550 \( \frac{ft⋅lb}{s} \) = 2200 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{85 \times 2200 \frac{ft⋅lb}{s}}{100} \) \( = \frac{187000 \frac{ft⋅lb}{s}}{100} \) = 1870 \( \frac{ft⋅lb}{s} \)

Which of the following is not true of a first-class lever?

51% Answer Correctly

	increases force
	increases distance
	decreases distance
	changes the direction of force

Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

65% Answer Correctly

	energy
	torque
	rotational direction
	force

Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

Which of the following is not a modulus of elasticity?

47% Answer Correctly

	shear modulus
	stretch modulus
	bulk modulus
	stress modulus

Solution

The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).