ASVAB Mechanical Comprehension Practice Test 584563 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.98
Score	0%	60%

Review

1 What is the mechanical advantage of this inclined plane if the length of the ramp is 32 ft. and the height of the green box is 4 ft.?

82% Answer Correctly

	9.5
	7.2
	8
	4

Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In this case, the effort distance is the length of the ramp and the resistance distance is the height of the green box:

MA = \( \frac{d_e}{d_r} \) = \( \frac{32 ft.}{4 ft.} \) = 8

2 What is the power output of a 5 hp engine that's 25% efficient?

39% Answer Correctly

	687.5 \( \frac{ft⋅lb}{s} \)
	5 \( \frac{ft⋅lb}{s} \)
	229.2 \( \frac{ft⋅lb}{s} \)
	343.8 \( \frac{ft⋅lb}{s} \)

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 5 hp x 550 \( \frac{ft⋅lb}{s} \) = 2750 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{25 \times 2750 \frac{ft⋅lb}{s}}{100} \) \( = \frac{68750 \frac{ft⋅lb}{s}}{100} \) = 687.5 \( \frac{ft⋅lb}{s} \)

An inclined plane increases ___________ to reduce ____________.

58% Answer Correctly

	force, power
	distance, power
	distance, force
	force, distance

Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.

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

	0.83 lbs
	810 lbs
	90 lbs
	45 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

What is the first step to solving a problem where multiple forces are acting on an object?

61% Answer Correctly

	calculate the total force
	calculate potential energy
	calculate kinetic energy
	calculate the net force

Solution

In mechanics, multiple forces are often acting on a particular object and, taken together, produce the net force acting on that object. Like force, net force is a vector quantity in that it has magnitude and direction.