FCTC Mechanical Reasoning Principles Questions and Answers 4

Question 1

A lever 10 feet long has its fulcrum 2 feet from one end. A 200 lb load is placed at the short end. What force must be applied at the long end to balance it?

Accepted Answer

50 lbs

Answer

Torque balance: Load × short arm = Effort × long arm → 200 × 2 = Effort × 8, so Effort = 400/8 = 50 lbs.

Question 2

Which of the following would cause a V-belt drive to slip on its pulley?

Accepted Answer

Insufficient belt tension

Answer

A V-belt requires adequate tension to generate the friction needed to transfer torque without slipping.

Question 3

An inclined plane is 12 feet long and rises 3 feet. What is its mechanical advantage?

Accepted Answer

4

Answer

Mechanical advantage of an inclined plane = length / height = 12 / 3 = 4.

Question 4

Two gears are in mesh. Gear A has 20 teeth and rotates at 600 RPM. Gear B has 60 teeth. What is the speed of Gear B?

Accepted Answer

200 RPM

Answer

Speed ratio = teeth of driver / teeth of driven = 20/60, so Gear B speed = 600 × (20/60) = 200 RPM.

Question 5

A pressure gauge on a boiler reads 150 PSI. If the boiler's safety valve is set to 175 PSI, what is the pressure margin before the valve opens?

Accepted Answer

25 PSI

Answer

Pressure margin = safety valve setting − current pressure = 175 − 150 = 25 PSI.

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FCTC Mechanical Reasoning Principles Questions and Answers 4