Final answer:
For an effective cutting stroke with a razor, it is recommended to use the blade at an angle, utilizing the principle that a smaller blade surface area results in higher pressure and more efficient cutting.
Step-by-step explanation:
To achieve the best cutting stroke with a razor, it is indeed beneficial for the razor to glide over the surface at an angle. This approach is backed by the principle that a sharp edge will apply more pressure on the material it is cutting due to the reduced surface area in contact with the material. The lesser the surface area, the greater the pressure exerted for the same amount of force, as pressure is defined as force per unit area.
As seen in the provided materials from Chapter 9, a sharpened knife has a smaller surface area which leads to higher pressure and more effective cutting. Applying this concept to a razor, maintaining an angle while cutting also utilizes a smaller surface area of the blade edge, ensuring a smoother and more efficient cut.
In real-world examples, similar principles are observed in Chapter 13 and 21, where blade design plays a crucial role in the efficiency and safety of their respective uses, such as in three-blade razors or wind turbine blades.