Question

A bodybuilder configures a leg-press apparatus (see figure) to a resistance of 1080 N (about 243 lb). She pushes the weight to her full extension and comes to rest.

a) What is the normal force on each of her feet?


(b) Assume she is able to move the push-plate of the leg-press machine at an acceleration of 0.50 m/s² for the first half of the displacement. What is the normal force on each foot during this period of acceleration? Assume the resistive force is due to a mass with weight of 1080 N hanging on the cable of the leg-press apparatus.

Answer 1

a) Normal force on each feet = 1080 / 2= 540 N

mass of feet = 1080/9.8= 110.204 kg

b) Normal force = weight of hanging mass ( 1080 ) + force causing acclerartio ( 110.204 x 0.5)= 1135. 102 N apprx