ASVAB Mechanical Comprehension Practice Test 673123 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.36
Score	0%	67%

Review

The standard unit of energy is the:

73% Answer Correctly

	Joule
	Watt
	Horsepower
	Volt

Solution

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).

The mass of an object correlates to the size of the object but ultimately depends on:

67% Answer Correctly

	gravity
	the object's potential energy
	the object's density
	the object's weight

Solution

Mass is a measure of the amount of matter in an object. In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.

3 If 35 lbs. of force is applied 8 ft. from the fulcrum at the blue arrow and the green box is 4 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

62% Answer Correctly

	70 lbs.
	23.33 lbs.
	0 lbs.
	280 lbs.

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 R_a, our missing value, and plugging in our variables yields:

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{35 lbs. \times 8 ft.}{4 ft.} \) = \( \frac{280 ft⋅lb}{4 ft.} \) = 70 lbs.

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

	90 lbs
	0.83 lbs
	45 lbs
	810 lbs

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. Plugging in the variables from this problem yields:

F_e x 3 ft. = 270 lbs x 0.5 ft
F_e = 135 ft-lb. / 3 ft
F_e= 45 lbs

The force required to initally get an object moving is __________ the force required to keep it moving.

76% Answer Correctly

	the same as
	higher than
	opposite
	lower than

Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).