hat power is expended by a weightlifter when lifting a 58- kg barbell a vertical distance of 0.70 m in a time interval of 1.9 s .
To find the power expended by the weightlifter while lifting the barbell, we can use the formula:
Power = Work / Time
First, let's find the work done by the weightlifter. Work is calculated using the formula:
Work = Force x Distance x cosθ
In this case, the force is equal to the weight of the barbell. The weight can be found using the formula:
Weight = mass x gravity
where the mass is 58 kg and gravity is approximately 9.8 m/s^2.
Weight = 58 kg x 9.8 m/s^2 = 568.4 N
Now, we can calculate the work:
Work = 568.4 N x 0.70 m x cos(0°)
Since the barbell is lifted vertically, the angle θ between the force and distance is 0°, and cos(0°) is equal to 1.
Work = 568.4 N x 0.70 m x 1 = 397.88 J (joules)
Now, we can calculate the power:
Power = 397.88 J / 1.9 s
Power = approximately 209.4 W (watts)
Therefore, the power expended by the weightlifter when lifting the barbell is approximately 209.4 watts.