Final answer:
The amount of work performed on a treadmill is affected by the slope, belt speed, and body weight of the individual. The work done lifting a book is dependent on the height of the shelf and the mass of the book. Efficiency of treadmill exercise would involve comparing work output to energy expenditure, such as oxygen consumption rate.
Step-by-step explanation:
The factors that affect the amount of work performed during treadmill exercise include both the slope of the treadmill walking surface and the speed of the treadmill belt. The height of the subject does not directly affect the work done, but the body weight of the subject does because work is a product of force (in this case, body weight acting as force due to gravity) and distance.
When it comes to the speed of an object rolling down an incline, the dominant factor is gravitational force, provided there is no friction. The work you do on a book when lifting it onto a shelf indeed depends on the height of the shelf and the mass of the book, but not on the path nor the time taken, assuming no other forces are acting on the book. It is because work is calculated as the product of the force exerted on the object (in this case, upward force to counteract gravity) and the vertical distance moved.