A weightlifter lifts a barbell (Fig.). List two forces that are acting on the barbell. Class 9

A weightlifter lifts a barbell (Fig.). List two forces that are acting on the barbell. Class 9

Pause and Ponder (Page 97)

Question 1.

A weightlifter lifts a barbell (Fig.). List two forces that are acting on the barbell. Are these forces balanced if the weightlifter keeps the barbell steady? Class 9

Answer:

Two forces acting on the barbell are:

(a) Gravitational force (weight): The Earth pulls the barbell downward.

(b) Upward force applied by the weightlifter:

She pushes the barbell upward.

Yes, these forces are balanced when the weightlifter keeps the barbell steady. Since the barbell is stationary, the net force on it is zero, meaning the two forces are equal in magnitude and opposite in direction.

Question 2.

Two players R and S are participating in an arm-wrestling match (Fig.). At the instant when the arms tilt to the front direction (out of the page towards you), are the forces exerted by the players balanced? If not, which player exerted the larger force? Class 9

Answer:

When the arms tilt to the front direction, the forces are NOT balanced. A net force is acting that caused the arms to move from their initial position. Since the arms moved in a direction associated with player R's push, player R exerted the larger force.