ASVAB Mechanical Comprehension Practice Test 639701 Results

Your Results Global Average
Questions 5 5
Correct 0 3.31
Score 0% 66%

Review

1

Friction between two or more solid objects that are not moving relative to each other is called:

73% Answer Correctly

kinetic friction

gravitational friction

dynamic friction

static friction
Solution

Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.

2 If a 70 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow and the green box is 2 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
26.25 lbs.
0 lbs.
105 lbs.
210 lbs.
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:

Rada = Rbdb

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

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{70 lbs. \times 3 ft.}{2 ft.} \) = \( \frac{210 ft⋅lb}{2 ft.} \) = 105 lbs.

3

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

force or distance

speed or power

force or speed

power or distance
Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

4

The mechanical advantage of a block and tackle is equal to which of the following?

69% Answer Correctly

the number of connecting ropes

the number of input forces

the number of loads

the number of pulleys
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.

5 What's the mechanical advantage of a wedge that's 2 inches wide and 4 inches long?
83% Answer Correctly
2.2
5
3
2
Solution

The mechanical advantage (MA) of a wedge is its length divided by its thickness:

MA = \( \frac{l}{t} \) = \( \frac{4 in.}{2 in.} \) = 2