Final answer:
The proper use of body mechanics when transferring a client from a bed to a wheelchair is achieved by keeping the back straight and using the leg muscles to lift, aligning with safe lifting principles.
Step-by-step explanation:
When a nurse is preparing to transfer a client from a bed to a wheelchair, demonstrating proper use of body mechanics involves keeping the back straight and using leg muscles to lift. This method reduces the stress on the spine since it minimizes the force required by the back muscles by utilizing the stronger leg muscles. It also aligns with the principles of physics that suggest lifting with a straight back and bending the knees to lower the center of gravity creates smaller forces in the back, which is a safer and more efficient lifting technique.