An athlete whose mass is 90.0 kg is performing weight-lifting exercises. Starting from the rest position, he lifts, with constant acceleration, a barbell that weighs 490 N. He lifts the barbell a distance of 0.60 m in 1.6 s. (a) Draw a clearly labeled free-body force diagram for the barbell and for the athlete. (b) Use the diagrams in part (a) and Newton’s laws to find the total force that his feet exert on the ground as he lifts the barbell.

Solution to 55P Step 1 Mass of the athlete=90kg Weight of the athlete =90x9.8=882N Weight of the barbell=490N Mass of the barbell=490/9.8=50Kg Force exerted on the ground by the athlete without the barbell=882N Force exerted on the ground by the athlete with the barbell=882+490=1372N Step 2 (A)