ASVAB Mechanical Comprehension Practice Test 820136 Results

Your Results Global Average
Questions 5 5
Correct 0 3.24
Score 0% 65%

Review

1

A screw is most like which of the following other simple machines?

50% Answer Correctly

block and tackle

first-class lever

wheel and axle

inclined plane


Solution

A screw is an inclined plane wrapped in ridges (threads) around a cylinder. The distance between these ridges defines the pitch of the screw and this distance is how far the screw advances when it is turned once. The mechanical advantage of a screw is its circumference divided by the pitch.


2

Which of the following statements about this pulley configuration is false?

48% Answer Correctly

Changes the direction of and multiplies the effort force

Mechanical advantage is the number of ropes that support the resistance

Only multiplies the effort force

This is a block and tackle pulley configuration


Solution

A block and tackle is a combination of one or more fixed pulleys and one or more movable pulleys where the fixed pulleys change the direction of the effort force and the movable pulleys multiply it. The mechanical advantage is equal to the number of times the effort force changes direction and can be increased by adding more pulley wheels to the system. An easy way to find the mechanical advantage of a block and tackle pulley system is to count the number of ropes that support the resistance.


3

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

89% Answer Correctly

wheel and axle

first-class lever

fixed pulley

block and tackle


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.


4

The force required to initally get an object moving is __________ the force required to keep it moving. 

76% Answer Correctly

opposite

lower than

the same as

higher than


Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).


5

Which of the following is the formula for gravitational potential energy?

61% Answer Correctly

\(PE = { 1 \over 2} mv^2\)

\(PE = { 1 \over 2} mg^2\)

\(PE = mg^2h\)

\(PE = mgh\)


Solution

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s2).