ASVAB Mechanical Comprehension Practice Test 587900 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.97
Score	0%	59%

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 input forces
	the number of loads
	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.

The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?

60% Answer Correctly

	conservation of mechanical energy
	work-energy theorem
	mechanical advantage
	Pascal's law

Solution

The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.

3 If the green box weighs 35 lbs. and 65 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow, how far from the fulcrum would the green box need to be placed to balance the lever?

55% Answer Correctly

	27.86 ft.
	175 ft.
	0 ft.
	9.29 ft.

Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

Solving for d_a, our missing value, and plugging in our variables yields:

d_a = \( \frac{R_bd_b}{R_a} \) = \( \frac{65 lbs. \times 5 ft.}{35 lbs.} \) = \( \frac{325 ft⋅lb}{35 lbs.} \) = 9.29 ft.

4 If the handles of a wheelbarrow are 2.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 130 lbs. load concentrated at a point 1.5 ft. from the axle?

52% Answer Correctly

	-2
	0
	260
	97.5

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 effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{130 \times 1.5}{2.0} \)
\( F_e = \frac{195.0}{2.0} \)
\( F_e = 97.5 \)

What type of load creates different stresses at different locations on a structure?

60% Answer Correctly

	non-uniformly distributed load
	dynamic load
	static uniformly distributed 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.