ASVAB Mechanical Comprehension Practice Test 548500 Results

Your Results Global Average
Questions 5 5
Correct 0 3.07
Score 0% 61%

Review

1

What type of load acts on a relatively small area of a structure?

75% Answer Correctly

concentrated load

impact load

non-uniformly distributed load

dynamic load
Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

2 If the green box weighs 25 lbs. and 10 lbs. of force is applied 7 ft. from the fulcrum at the blue arrow, how far from the fulcrum would the green box need to be placed to balance the lever?
55% Answer Correctly
2.8 ft.
11.2 ft.
3 ft.
1.4 ft.
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 da, our missing value, and plugging in our variables yields:

da = \( \frac{R_bd_b}{R_a} \) = \( \frac{10 lbs. \times 7 ft.}{25 lbs.} \) = \( \frac{70 ft⋅lb}{25 lbs.} \) = 2.8 ft.

3

A a seesaw / teeter-totter is an example of which of the following?

69% Answer Correctly

inclined plane

second-class lever

first-class lever

third-class lever
Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

4 How much work can a 4 hp engine do in 5 seconds?
52% Answer Correctly
0 ft⋅lb
8 ft⋅lb
11000 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:
\( W = 4 hp \times 550 \frac{ft⋅lb}{s} \times 5s = 11000 ft⋅lb \)
5

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

810 lbs

45 lbs

90 lbs

0.83 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: Fede = Frdr. Plugging in the variables from this problem yields:

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