ASVAB Mechanical Comprehension Practice Test 58114 Results

Your Results Global Average
Questions 5 5
Correct 0 2.84
Score 0% 57%

Review

1

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

its direction

its weight

its speed

its mass


Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.


2

Which of the following is not a modulus of elasticity?

47% Answer Correctly

bulk modulus

shear modulus

stress modulus

stretch modulus


Solution

The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).


3

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

61% Answer Correctly

increase, increase

decrease, decrease

increase, decrease

decrease, 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.


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 pulleys

the number of loads

the number of input forces


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 If the handles of a wheelbarrow are 2.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 160 lbs. load concentrated at a point 0.5 ft. from the axle?
52% Answer Correctly
None of these is correct
25.7
800
32

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:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{160 \times 0.5}{2.5} \)
\( F_e = \frac{80.0}{2.5} \)
\( F_e = 32 \)