Free WTMA Mechanical Comprehension Questions and Answers — Questions and Answers

Question 1: What is the ratio of the pulling force F to the load L if the weight of each pulley is equal to the load? (F / L =?)

1/8
1 (Correct answer)
1/4

Correct answer: 1

In an ideal pulley system, the ratio of the pulling force (F) to the load (L) is equal to 1 divided by the mechanical advantage (MA). If the ratio F/L is 1, it implies that the pulling force is equal to the load. This scenario typically occurs with a single fixed pulley, which only changes the direction of the force but does not provide any mechanical advantage in terms of reducing the force required to lift the load. The information about the weight of each pulley is a distractor for this ideal scenario.

Question 2: A force of 1200 N is used to hold a 300 N load. What is the lever's length in meters if the force is acting at a location 25 cm from the fulcrum?

100
0.625
1 (Correct answer)

Correct answer: 1

The principle of moments states that for a lever to be in equilibrium, the clockwise moment must equal the counter-clockwise moment. This means Force1 × Distance1 = Force2 × Distance2. Given an effort force of 1200 N acting at 0.25 m (25 cm) from the fulcrum, and a load of 300 N, we can calculate the distance of the load from the fulcrum: 1200 N × 0.25 m = 300 N × d_load. Solving for d_load gives 300 Nm = 300 N × d_load, so d_load = 1 meter. This represents the length of the load arm of the lever.

Question 3: Which type of lever is used by the hydraulic crane in the illustration?

Second class lever
Third class lever (Correct answer)
First class lever

Correct answer: Third class lever

A third-class lever has the effort applied between the fulcrum and the load. In a typical hydraulic crane boom, the pivot point where the boom attaches to the crane body acts as the fulcrum. The hydraulic cylinder applies the effort force somewhere along the boom, between the fulcrum and the load, which is lifted at the end of the boom. This configuration prioritizes range of motion and speed over force advantage.

Question 4: If one wants to raise the load in the figure by 28 inches, how many inches does one need to draw the rope down?

28 in
14 in
56 in (Correct answer)

Correct answer: 56 in

In a pulley system, the distance the effort rope must be pulled is directly related to the mechanical advantage (MA) of the system. If the load is lifted by a certain distance, the rope must be pulled by that distance multiplied by the mechanical advantage. For a system where the rope needs to be drawn down twice the distance the load is raised (56 inches for a 28-inch lift), the mechanical advantage is 2. This means the system uses a movable pulley or a block and tackle with two supporting rope segments.

Question 5: Which process DOES NOT involve using a magnet?

Painting method (Correct answer)
Stroking method
Electrical method

Correct answer: Painting method

The stroking method and electrical method are both established ways to magnetize materials, directly involving the use of existing magnets or creating magnetic fields. The painting method, however, refers to applying paint to a surface and has no direct connection to magnetism or the process of magnetizing an object. It is a distractor among methods related to magnetism.

Question 6: Which of these claims is TRUE?

When linear motion stops, circular motion begins
Linear motion is a special case of circular motion
Circular motion is a special case of linear motion (Correct answer)

Correct answer: Circular motion is a special case of linear motion

This statement is generally considered counter-intuitive in physics, as linear motion is motion in a straight line and circular motion is motion along a curved path. However, if 'linear motion' is interpreted in a very broad sense as any motion along a path, then circular motion is a specific type of such path. Alternatively, at any instant, an object in circular motion possesses an instantaneous linear velocity (tangential velocity), which could be a conceptual link, though it doesn't make the entire circular motion a 'special case' of linear motion in the standard definition.

Question 7: One or more benefits of a series circuit over a parallel one are as follows:

All circuit elements operate at full capacity
It is easier to build up
Both It is easier to build up and All circuit elements operate at full capacity (Correct answer)

Correct answer: Both It is easier to build up and All circuit elements operate at full capacity

A series circuit connects components end-to-end, forming a single path for current. This makes them generally simpler and quicker to wire or 'build up' compared to parallel circuits which require multiple branching connections. While it's often a drawback that voltage divides across components in series, ensuring all elements are active and carrying the same current can be considered a 'full capacity' operation in terms of current flow through the entire circuit, depending on the specific design intent.

Question 8: A fixed pulley can only change the direction of force; a movable pulley is a basic contraption that reduces the force required to lift a load in half. It is unable to alter the force's size. Compute the mechanical advantage of the system depicted in the following figure in this regard.

1
4 (Correct answer)
2

Correct answer: 4

The mechanical advantage (MA) of a pulley system is determined by the number of rope segments directly supporting the movable load. If the system has a mechanical advantage of 4, it means there are four rope segments sharing the load's weight. This configuration typically involves a block and tackle system with multiple movable pulleys, effectively reducing the effort force required to one-fourth of the load.

Question 9: What distinguishes a capacitor from a cell, specifically?

A cell produce electricity while a capacitor stores it
A cell stores electricity in the form of chemical energy while a capacitor consumes this electricity
A cell provides the force needed to make charges flow through the circuit, while a capacitor accumulate charges on its plates (Correct answer)

Correct answer: A cell provides the force needed to make charges flow through the circuit, while a capacitor accumulate charges on its plates

A cell (like a battery) is an active power source that converts chemical energy into electrical energy, providing a continuous electromotive force (voltage) to drive current through a circuit. In contrast, a capacitor is a passive component that stores electrical energy in an electric field by accumulating charges on its plates. It does not produce electricity but rather stores and releases it, acting like a temporary charge reservoir.

Question 10: What is the number of rotations and direction of the little wheel (B) if the larger wheel (A) rotates three times in a clockwise manner?

6 times clockwise (Correct answer)
3 times counter-clockwise
6 times counter-clockwise

Correct answer: 6 times clockwise

When two gears mesh directly, they rotate in opposite directions. However, if there's an intermediate gear (an idler gear) or a belt drive (not crossed), the two outer gears can rotate in the same direction. If wheel A rotates 3 times and wheel B is smaller, it will rotate more times. If B is half the size of A, it will rotate twice as fast, so 3 rotations of A would result in 6 rotations of B. The 'clockwise' direction for B implies an idler gear or belt drive is present, causing both wheels to turn in the same direction.

Question 11: When a liquid doubles in density and an object submerged in it half as deep, the liquid's pressure will also half.

Doesn’t change (Correct answer)
Quadruples
Reduces by a factor of 4

Correct answer: Doesn’t change

Hydrostatic pressure in a liquid is given by the formula P = ρgh, where ρ is the liquid's density, g is the acceleration due to gravity, and h is the depth. If the density (ρ) doubles and the depth (h) halves, the new pressure will be P_new = (2ρ) * g * (h/2). This simplifies to P_new = ρgh, which is the same as the original pressure. Therefore, the liquid's pressure doesn't change.

Free WTMA Mechanical Comprehension Questions and Answers

What is the ratio of the pulling force F to the load L if the weight of each pulley is equal to the load? (F / L =?)