BARB Mechanical Comprehension

Question 1

A lever has its fulcrum in the middle. A 10 kg load is placed 2 m to the left. Where must a 5 kg effort be placed on the right to balance it?

Accepted Answer

4 m

Answer

Moment = Force × Distance; 10 × 2 = 20 Nm; 5 × d = 20; d = 4 m.

Question 2

Two gears are meshed together. Gear A has 20 teeth and Gear B has 40 teeth. If Gear A turns at 100 rpm, how fast does Gear B turn?

Accepted Answer

50 rpm

Answer

Gear ratio = 20/40 = 1/2; Gear B turns at 100 × (1/2) = 50 rpm.

Question 3

A pulley system uses two pulleys. What effect does adding a second pulley have?

Accepted Answer

It halves the effort needed to lift a load

Answer

A two-pulley system provides a mechanical advantage of 2, halving the effort required.

Question 4

Water flows through a pipe that narrows from 4 cm to 2 cm in diameter. What happens to the water's speed?

Accepted Answer

It quadruples

Answer

Cross-sectional area is proportional to diameter squared; halving diameter reduces area by 4×, so speed increases 4×.

Question 5

A soldier uses a ramp to load a heavy crate onto a truck. What mechanical advantage does the ramp provide?

Accepted Answer

It increases the distance but reduces the required force

Answer

A ramp (inclined plane) reduces the force required by spreading the work over a longer distance.

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