ASVAB Mechanical Comprehension Practice Test 136336 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.67
Score	0%	53%

Review

1 If the handles of a wheelbarrow are 2.0 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 170 lbs. force lift?

47% Answer Correctly

	170
	340
	628.2
	86.6

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:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{170 \times 2.0}{1.0} \)
\( F_r = \frac{340.0}{1.0} \)
\( F_r = 340 \)

2 If the green box weighs 15 lbs. and is 3 ft. from the fulcrum, how far from the fulcrum would a 15 lbs. weight need to be placed to balance the lever?

61% Answer Correctly

	1 ft.
	3 ft.
	0 ft.
	12 ft.

Solution

To balance this lever the torques on each side of the fulcrum 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 left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

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

d_b = \( \frac{R_ad_a}{R_b} \) = \( \frac{15 lbs. \times 3 ft.}{15 lbs.} \) = \( \frac{45 ft⋅lb}{15 lbs.} \) = 3 ft.

Sam can do 50 ft. lb. of work in 2 minutes and 5 seconds. What would Sam have to do to increase his power output?

64% Answer Correctly

	do 25 ft. lb. of work in 2 minutes 5 seconds
	do 100 ft. lb. of work in 4 minutes 12 seconds
	do the work in 2 minutes
	do the work in 3 minutes

Solution

Power is the rate of doing work or \(\frac{W}{t}\). To increase power, increase the work being done in the same amount of time or do the same amount of work in less time.

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

40% Answer Correctly

	higher than
	lower than
	the same as
	opposite

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.

A wedge converts force applied to its blunt end into force __________ its inclined surface.

57% Answer Correctly

	along
	perpendicular to
	parallel to
	opposite to

Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.