Final answer:
The student's question about pushing with a machine is related to normal force and gravity in Physics. The normal force can result in a person feeling an upward push that is several times their body weight. Proper lifting techniques are essential to minimize the forces on the spine.
Step-by-step explanation:
When discussing the forces on the body and how much one would be pushing with a machine, we are delving into Physics, specifically the concept of normal force and gravity. The provided information indicates that the normal force exerted on a person by a machine can be multiple times greater than the force of gravity alone. For instance, when the normal force is three times a person's weight, it means that the individual would feel significantly heavier due to the additional normal force applied, which is contrary to standing erect where the force is equal to the individual's weight.
The difficulty with the spine experiencing forces is not that they are necessarily greater than those in the hips, knees, and ankles, but that the spine is less equipped to handle such forces. Proper lifting techniques, which involve keeping the back straight and using the legs to lift, can greatly reduce the forces applied to the spine. The exertion of force, whether it's an athlete applying force in an exercise or airmen pushing a Humvee uphill, demonstrates how forces larger than our weight are frequently encountered and managed in various circumstances.
In conclusion, the amount of force one would push with a machine would depend on the scenario and could indeed be as much as - or multiple times - their weight, especially when considering the normal force being exerted.