ASVAB Mechanical Comprehension Practice Test 48098 Results

Your Results Global Average
Questions 5 5
Correct 0 3.09
Score 0% 62%

Review

1 How much work can a 4 hp engine do in 10 seconds?
52% Answer Correctly
16 ft⋅lb
0 ft⋅lb
22000 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:
\( W = 4 hp \times 550 \frac{ft⋅lb}{s} \times 10s = 22000 ft⋅lb \)
2

Two gears are connected and the smaller gear drives the larger gear. The speed of rotation will __________ and the torque will __________.

61% Answer Correctly

increase, decrease

decrease, increase

decrease, decrease

increase, increase
Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

3

The mechanical advantage of connected gears is proportional to which characteristic of the gears?

73% Answer Correctly

diameter

circumference

speed

number of teeth
Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear.  For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

4 If the handles of a wheelbarrow are 0.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 100 lbs. load concentrated at a point 0.5 ft. from the axle?
52% Answer Correctly
568.6
0
100
-38.1
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. In this problem we're looking for effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{100 \times 0.5}{0.5} \)
\( F_e = \frac{50.0}{0.5} \)
\( F_e = 100 \)
5

A fixed pulley has a mechanical advantage of:

68% Answer Correctly

1

-1

0

2
Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.