Explanation:
(A)
-With the barbell at rest- Both forces are equal
When the barbell is at rest then in this condition both forces are equal. The force exerted by the weight lifter on the barbell is equal to the force exerted by the barbell on the weight lifter.
(B)
-With the barbell moving upward- Forces are equal
When the barbell is moved upward by the weight lifter then the force exerted on the barbell by the weight lifter is greater than the gravitational force exerted on the barbell.
(C)
-With the barbell moving downward-Forces are equal
When the barbell is moved downward by the weight lifter then the force exerted on the barbell due to gravity is greater than the force exerted by the weight lifter on the barbell.