ASVAB Mechanical Comprehension Practice Test 642337 Results

Your Results Global Average
Questions 5 5
Correct 0 3.68
Score 0% 74%

Review

1

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

89% Answer Correctly

fixed pulley

block and tackle

wheel and axle

first-class lever
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.

2

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

73% Answer Correctly

speed

number of teeth

circumference

diameter
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.

3

Sam can do 50 ft. lb. of work in 2 minutes and 5 seconds. What would Sam have to do to increase his power output?

64% Answer Correctly

do 25 ft. lb. of work in 2 minutes 5 seconds

do 100 ft. lb. of work in 4 minutes 12 seconds

do the work in 3 minutes

do the work in 2 minutes
Solution

Power is the rate of doing work or \(\frac{W}{t}\). To increase power, increase the work being done in the same amount of time or do the same amount of work in less time.

4 If the green arrow in this diagram represents 1050 ft⋅lb of work, how far will the box move if it weighs 210 pounds?
72% Answer Correctly
0 ft.
105 ft.
42 ft.
5 ft.
Solution
The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

Win = Wout
Feffort x deffort = Fresistance x dresistance

In this problem, the effort work is 1050 ft⋅lb and the resistance force is 210 lbs. and we need to calculate the resistance distance:

Win = Fresistance x dresistance
1050 ft⋅lb = 210 lbs. x dresistance
dresistance = \( \frac{1050ft⋅lb}{210 lbs.} \) = 5 ft.

5 If you lift a 18 lbs. rock 2 ft. from the ground, how much work have you done?
71% Answer Correctly
36 ft⋅lb
18 ft⋅lb
9 ft⋅lb
20 ft⋅lb
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 18 \times 2 \)
\( W = 36 \)