SIFT Mechanical Comprehension Questions and Answers 3

Question 1

If a wheel with radius 3 feet is connected to an axle with radius 1 foot, what is the mechanical advantage?

Accepted Answer

3

Answer

The wheel and axle mechanical advantage = radius of wheel / radius of axle = 3/1 = 3. Turning the wheel requires less force than turning the axle directly.

Question 2

What happens to the speed of a fluid when it flows from a wider pipe into a narrower pipe (Bernoulli's principle)?

Accepted Answer

Speed increases and pressure decreases

Answer

By the continuity equation and Bernoulli's principle, fluid speed increases as it flows into a narrower section, and pressure decreases correspondingly.

Question 3

In a series electrical circuit with two resistors of 4Ω and 6Ω connected to a 20V battery, what is the total current?

Accepted Answer

2 A

Answer

In a series circuit, total resistance = R₁ + R₂ = 4 + 6 = 10Ω. Current I = V/R = 20/10 = 2 A.

Question 4

What does a 'shear pin' do in a mechanical system?

Accepted Answer

Intentionally breaks under excessive load to protect more expensive components

Answer

A shear pin is a deliberately weak fastener designed to break (shear) at a predetermined force, protecting more critical and expensive components from overload damage.

Question 5

A ramp (inclined plane) is 10 feet long and 2 feet high. What is the mechanical advantage?

Accepted Answer

5

Answer

Mechanical advantage of an inclined plane = length of slope / height = 10 / 2 = 5. You need only 1/5 the force to push an object up the ramp as you would to lift it straight up.

SIFT Exam Practice Test

SIFT Exam Practice Test

SIFT Mechanical Comprehension Questions and Answers 3