ASVAB Mechanical Comprehension Practice Test 827147 Results

Your Results Global Average
Questions 5 5
Correct 0 3.30
Score 0% 66%

Review

1 If you lift a 49 lbs. rock 43 ft. from the ground, how much work have you done?
71% Answer Correctly
None of these is correct
92 ft⋅lb
2107 ft⋅lb
1032 ft⋅lb
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 49 \times 43 \)
\( W = 2107 \)
2 If the handles of a wheelbarrow are 2.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 200 lbs. load concentrated at a point 1.0 ft. from the axle?
52% Answer Correctly
87.9
55.5
100
200
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:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{200 \times 1.0}{2.0} \)
\( F_e = \frac{200.0}{2.0} \)
\( F_e = 100 \)
3

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

48% Answer Correctly

Changes the direction of and multiplies the effort force

This is a block and tackle pulley configuration

Only multiplies the effort force

Mechanical advantage is the number of ropes that support the resistance
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.

4

On Earth, acceleration due to gravity (g) is approximately __________. 

81% Answer Correctly

1 m/s2

9.8 m/s2

1 m/s

6.67 x 10-11 m/s2
Solution

Newton's Law of Univeral Gravitation defines the general formula for the attraction of gravity between two objects:  \(\vec{F_{g}} = { Gm_{1}m_{2} \over r^2}\) . In the specific case of an object falling toward Earth, the acceleration due to gravity (g) is approximately 9.8 m/s2. 

5

A watt is the unit for which of the following?

71% Answer Correctly

mechanical advantage

power

work

energy
Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.