ASVAB Mechanical Comprehension Practice Test 371458 Results

Your Results Global Average
Questions 5 5
Correct 0 3.40
Score 0% 68%

Review

1 If 35 lbs. of force is applied 7 ft. from the fulcrum at the blue arrow and the green box is 3 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
62% Answer Correctly
27.22 lbs.
5 lbs.
81.67 lbs.
20.42 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:

Rada = Rbdb

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

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{35 lbs. \times 7 ft.}{3 ft.} \) = \( \frac{245 ft⋅lb}{3 ft.} \) = 81.67 lbs.

2 What's the mechanical advantage of a wedge that's 4 inches wide and 16 inches long?
83% Answer Correctly
5.5
1
3.6
4
Solution

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

MA = \( \frac{l}{t} \) = \( \frac{16 in.}{4 in.} \) = 4

3

The steering wheel of a car is an example of which type of simple machine?

89% Answer Correctly

fixed pulley

first-class lever

block and tackle

wheel and axle
Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

4 How much work can a 4 hp engine do in 2 seconds?
52% Answer Correctly
8 ft⋅lb
2 ft⋅lb
4400 ft⋅lb
1 ft⋅lb
Solution
Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 4 hp \times 550 \frac{ft⋅lb}{s} \times 2s = 4400 ft⋅lb \)
5

The measure of how much of the power put into a machine is turned into movement or force is called:

56% Answer Correctly

power

mechanical advantage

force multiplication

efficiency
Solution

The efficiency of a machine describes how much of the power put into the machine is turned into movement or force. A 100% efficient machine would turn all of the input power into output movement or force. However, no machine is 100% efficient due to friction, heat, wear and other imperfections that consume input power without delivering any output.