Applying Newton's Second Law - Conceptual Example 5.6-1

 

A weightlifter squats motionless on a scale with a barbell held on her shoulders. First the weightlifter stands up and then she lifts the barbell up and over her head ultimately holding the barbell motionless. If the woman's weight is 120 lb and the barbell's total weight is 70 lb, answer the following questions.

 

 

What does the scale read when the weightlifter is initially squatting on the scale?

 

70 lb
120 lb
190 lb
210 lb

 

 

 

 

 

What does the scale read when the weightlifter, after standing, moves the barbells up with an acceleration of 9 ft/s²?

 

70 lb
120 lb
190 lb
210 lb

 

 

 

 

 

What does the scale read when the weightlifter has the barbell up over her head?

 

70 lb
120 lb
190 lb
210 lb