This section of the U.S. Army's SIFT (Selection Instrument for Flight Training) exam tests your knowledge of basic physics, electrical, and mechanical theories.

Mechanical Comprehension questions focus on topics such as force, friction, current, fluid, pressure, pulleys, gears, screws, engines, and other machine operations.  You must familiarize yourself with physics, basic electronics, and mechanics concepts.

SIFT Mechanical Comprehension Practice Test

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25 Questions

1. Which of the following are not ways to increase the torque applied to a wrench?

increase the forceangle the force toward the centerincrease the length from the center to the applied force

2. Adding salt to water raises its density. Will salt water have a lower, higher, or the same specific gravity than 1?

higherthe samelower

3. A ball is thrown horizontally off a cliff at the same time that an identical ball is dropped off a cliff. How long after the dropped ball hits the ground will the thrown ball hit?

they will hit at the same timeapproximately 2 seconds afterapproximately 1 second after

4. River water enters a section where the water spreads out into a wide, deep area. Is the water likely to speed up, slow down, or remain at a constant speed?

speed upslow downremain at a constant speed

5. A cannon fires off a ship up towards a mountain range. Neglecting air resistance, where will the velocity of the projectile be greatest?

Halfway to the mountainsAs it impacts the mountainsExiting the muzzle

6. These pulleys are connected by belts. Which pulley travels the fastest?

Pulley APulley BPulley C

7. Two identical pistons are connected by a pipe. What is the mechanical advantage of the piston system?

0.512

8. If the resistors in the circuits are identical, which circuit will have the greatest overall resistance?

circuit Acircuit A and B have the same overall resistancecircuit B

9. A ball is thrown straight into the air with an initial kinetic energy of 100 ft-lb. What is the potential energy of the ball at half of the height of the flight path?

50 ft-lb66 ft-lb33 ft-lb

10. An increase in mechanical advantage with a set motion for the load and a set applied force necessitates an increase in _______ the applied force?

the distance traveled bythe angle of action ofthe potential energy behind

11. Which of these wrenches is likely to provide the greatest torque with a set force?

wrench Bwrench Aboth wrenches will provide the same torque

12. A solid substance melts at -21°C. If the object is known to change phase at 81°C, will the object be a solid, liquid, or gas at 90°C?

liquidsolidgas

13. Where should the fulcrum be located to balance this beam?

exactly between the two massescloser to the large masscloser to the small mass

14. Two gears (30 and 18 teeth) mesh. If the smaller gear rotates 3 times, how many times will the larger gear rotate?

1.8 times1.6 times3 times

15. Which color will absorb the most radiation?

blackgreendark yellow

16. A windlass drum has two sections with different circumferences. When winding the drum, one side of the rope winds around the large section and the other unwinds from the small section. If the large section of the drum has a circumference of 3.5 ft and the other section has a circumference of 1 ft, how far will the weight lift with two full turns of the drum?

2.5 feet4.5 feet9 feet

17. The cam rotates at 5 rpm. How many times will the follower (needle) move up and down in a minute?

2014072

18. A pendulum swings back and forth once per second. The pendulum is shortened by removing half of the string. The new frequency is 1.4 Hz (Hz=1/sec). How often will the pendulum swing back and forth in a minute?

847292

19. A vacuum tank is held by weights at a depth of 50 feet underwater. If the tank is raised to a depth of 25 feet, will the pressure on the walls of the tank increase, decrease, or stay the same?

stay the samedecreaseincrease

20. Which orientation will require more force to pull?

with the rope parallel to the tableboth orientations are equalwith the rope at an angle to the table

21. Which of the following is true of this circuit?

there is no currentthe current is the same everywherethe voltage is the same everywhere

22. If Gear A is traveling at 10 rpm, how many times will Gear C rotate in 3 minutes?

1.7 times30 times3 times

23. Which of the following is an example of convective heat transfer?

a man burns his hand on a hot pota man gets a sun burna man burns his hand in steam

24. The larger piston has four times as much horizontal area as the smaller piston. If the small piston is compressed 8 inches, how far will the larger piston move?

8 inches32 inches2 inches

25. A ball is pushed down into a vertical spring. The ball is released and flies upward. Which best describes the states of energy the ball underwent?

kinetic energy to potential energyconvective energy to potential energypotential energy to kinetic energy