ASVAB Mechanical Comprehension Practice Test 474444 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.93
Score	0%	59%

Review

A fixed pulley has a mechanical advantage of:

68% Answer Correctly

	1
	-1
	0
	2

Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

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 input forces
	the number of connecting ropes

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.

3 If the handles of a wheelbarrow are 0.5 ft. from the wheel axle and the load is concentrated at a point 1.0 ft. from the axle, how many pounds of load will a 140 lbs. force lift?

47% Answer Correctly

	-14
	140
	72.6
	70

Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: F_ed_e = F_rd_r. In this problem we're looking for resistance force:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{140 \times 0.5}{1.0} \)
\( F_r = \frac{70.0}{1.0} \)
\( F_r = 70 \)

Normal force is generally equal to the __________ of an object.

61% Answer Correctly

	weight
	density
	coefficient of friction
	mass

Solution

Normal force arises on a flat horizontal surface in response to an object's weight pressing it down. Consequently, normal force is generally equal to the object's weight.

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).