OAR OAR Mechanical Comprehension: Simple Machines 5

Question 1

A lever balances when the torque on each side is equal. If a 60 N load sits 2 m from the fulcrum, what effort is needed 4 m from the fulcrum?

Accepted Answer

30 N

Answer

Torque balance: effort × 4 = 60 × 2, so effort = 120/4 = 30 N.

Question 2

Which of the following is NOT a simple machine?

Accepted Answer

Spring

Answer

The six simple machines are lever, wheel and axle, pulley, inclined plane, wedge, and screw — a spring is not one of them.

Question 3

A block and tackle system with 3 movable pulleys and 3 fixed pulleys has approximately what mechanical advantage?

Accepted Answer

6

Answer

A block and tackle with 3 movable pulleys provides a mechanical advantage of 6 (twice the number of movable pulleys).

Question 4

When you tighten a jar lid using your fingers, the lid acts as which component of a wheel and axle?

Accepted Answer

The axle

Answer

The jar lid is the axle (smaller radius); your hand gripping the outside acts as the wheel (larger radius) applying torque.

Question 5

An inclined plane has a mechanical advantage of 5. If the load weighs 300 N, how much effort force is required (ignoring friction)?

Accepted Answer

60 N

Answer

Effort = load / MA = 300 / 5 = 60 N.

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