Weight Lifter: Equal Force to Barbell Weight

What is the relationship between the force exerted by the weight lifter and the weight of the 115-kg barbell?

1) The force exerted by the lifter is greater than the weight of the barbell.

2) The force exerted by the lifter is less than the weight of the barbell.

3) The force exerted by the lifter is equal to the weight of the barbell.

Main Answer:

The force exerted by the weight lifter is equal to the weight of the 115-kg barbell (Option 3).

The force exerted by the weight lifter is determined by the principle of Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. In this case, the weight lifter exerts an upward force on the barbell to lift it. The force exerted by the lifter is equal to the weight of the barbell, and this is due to the equilibrium between the gravitational force acting on the barbell (its weight) and the force exerted by the lifter to counteract it.

The weight of the 115-kg barbell can be calculated using the formula: Weight = mass × gravitational acceleration (Weight = m × g), where 'm' is the mass of the barbell and 'g' is the acceleration due to gravity (approximately 9.81 m/s²).

Weight of the barbell = 115 kg × 9.81 m/s² ≈ 1128.15 N.

To lift the barbell off the ground and keep it in a stationary position, the lifter must exert an equal and opposite force of 1128.15 N, which is the weight of the barbell. Therefore, the force exerted by the lifter is equal to the weight of the barbell, making Option 3 the correct answer.

Therefore, the correct option is: 3) The force exerted by the lifter is equal to the weight of the barbell.