In basic mechanics of simple machines such as levers and pulleys, which of the following statements is true for all real simple machines?

Introduction / Context:
Simple machines such as levers, pulleys, inclined planes, screws and wheels and axles are fundamental tools used to make tasks more manageable. They do not remove the requirement to do work, but they help us apply smaller forces over longer distances or in more convenient directions. Understanding what is always true about simple machines helps clarify common misconceptions about work, energy and mechanical advantage. This question tests your understanding of the relationship between work input, work output and the purpose of simple machines.

Given Data / Assumptions:

• Work is defined as force multiplied by displacement in the direction of the force.
• Simple machines can change the magnitude or direction of an applied force.
• Real machines are not frictionless and always have some energy losses.
• Mechanical advantage relates output force to input force, but does not create energy.

Concept / Approach:
The main purpose of a simple machine is to make it easier or more convenient to perform a task, often by allowing a smaller input force over a greater distance or by changing the direction of the applied force. For example, a lever lets you lift a heavy object with less effort, and a pulley can allow you to pull down to lift a load up. However, due to friction and other losses, the total work you put into a real machine is always slightly greater than the useful work you get out. In an idealised, frictionless machine, work input equals work output, but in reality, work input is greater than output. Both of these statements are true for real simple machines: they make work easier in terms of effort, and they require more input work than the useful output due to losses.

Step-by-Step Solution:
Step 1: Recall that simple machines provide mechanical advantage by amplifying force or changing its direction.Step 2: Understand that making work easier usually means reducing the required input force, even if the distance over which the force is applied increases.Step 3: Recognise that in an ideal machine with no friction, work input equals work output (ignoring losses).Step 4: Note that in real machines, friction in moving parts and deformation losses cause some input energy to convert into heat and sound.Step 5: Therefore, in real machines, work input must be greater than useful work output, because some energy is lost.Step 6: Combine these ideas to see that both statements A and B correctly describe real simple machines.Step 7: Conclude that the option stating both A and B are true is correct.

Verification / Alternative check:
Consider using a pulley to lift a heavy object. You apply a force over a long distance of rope, which feels easier than lifting straight up, showing that the pulley makes the task easier. However, if you carefully measure the energy, you will find that the work you do pulling the rope is slightly more than the gain in gravitational potential energy of the load. The difference appears as heat in the rope and pulley bearings. Similar reasoning applies to levers, jacks and inclined planes. Practical efficiency values for machines are always less than 100 percent, reinforcing that input work exceeds output work in real cases.

Why Other Options Are Wrong:
Option A alone is partly true, but the question asks which statement is true of all real simple machines, and we also know that friction makes input work exceed output work, so we need both ideas. Option B alone ignores the purpose of simple machines, which is to make work easier in terms of force and direction. Option D is completely wrong, as no machine can create energy from nothing; this would violate conservation of energy. Machines can only transform and transfer energy, not generate it spontaneously.

Common Pitfalls:
Students often mistakenly believe that simple machines reduce the total amount of work needed. In reality, they change how the work is done, but due to friction, you often have to do slightly more work than the useful output. Another misconception is that a machine with very large mechanical advantage might violate conservation of energy. Remember that any increase in force comes with a proportional increase in distance or time, keeping total work balanced, except for losses. To avoid these errors, focus on both the helpful change in force and the unavoidable energy losses in real machines.

Final Answer:
For all real simple machines, it is true that they make work easier by changing force and direction, and that work input is greater than useful work output due to friction, so both statements together are correct.