ASVAB Mechanical Comprehension Practice Test 176277 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.27
Score	0%	65%

Review

1 If the green box weighs 70 lbs. and is 1 ft. from the fulcrum, how far from the fulcrum would a 30 lbs. force need to be applied to balance the lever?

58% Answer Correctly

	0 ft.
	0.78 ft.
	9.33 ft.
	2.33 ft.

Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

Solving for d_b, our missing value, and plugging in our variables yields:

d_b = \( \frac{R_ad_a}{R_b} \) = \( \frac{70 lbs. \times 1 ft.}{30 lbs.} \) = \( \frac{70 ft⋅lb}{30 lbs.} \) = 2.33 ft.

When it comes to force, mass and acceleration have what kind of relationship?

66% Answer Correctly

	exponential
	inverse
	logarithmic
	linear

Solution

Newton's Second Law of Motion states that "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This Law describes the linear relationship between mass and acceleration when it comes to force and leads to the formula F = ma or force equals mass multiplied by rate of acceleration.

3 A = 4 ft., the green box weighs 40 lbs., and the blue box weighs 60 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	0.89 ft.
	2.67 ft.
	0.67 ft.
	8 ft.

Solution

In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

f_Ad_A = f_Bd_B

For this problem, the equation becomes:

40 lbs. x 4 ft. = 60 lbs. x d_B

d_B = \( \frac{40 \times 4 ft⋅lb}{60 lbs.} \) = \( \frac{160 ft⋅lb}{60 lbs.} \) = 2.67 ft.

Which of the following surfaces would have the highest coefficient of friction?

77% Answer Correctly

	marble
	steel
	concrete
	ice

Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

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

61% Answer Correctly

	decrease, decrease
	increase, increase
	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.