A weightlifter holding a 500 kg barbell waist high carries the barbell at a constant height and a constant speed to a rack 2 m away, and places the barbell on the rack at the same height at which he was carrying it. How much work does the weightlifter do on the barbell?
Constant height? He did not work against gravity, then.
To calculate the work done by the weightlifter on the barbell, we need to use the formula:
Work = Force x Distance x cos(theta)
In this case, the force is the weight of the barbell, which is equal to its mass multiplied by the acceleration due to gravity (F = mg), where g is approximately 9.8 m/s^2.
The distance is the horizontal distance traveled by the weightlifter, which is given as 2 m in the question.
The angle theta between the applied force and the direction of motion is zero since the weightlifter carries the barbell at a constant height and a constant speed, which means the vertical displacement is zero.
Now let's calculate the work done by the weightlifter on the barbell step by step:
1. Calculate the force:
The mass of the barbell is given as 500 kg.
So the force (F) = 500 kg x 9.8 m/s^2 = 4900 N.
2. Calculate the work:
Using the formula Work = Force x Distance x cos(theta),
Work = 4900 N x 2 m x cos(0) = 9800 J (joules).
Therefore, the weightlifter does 9800 joules of work on the barbell.