Show that 480 W of power is expended by a weightlifter when lifting a 60-kg barbell a vertical distance of 1.2 m in a time interval of 1.5 s.
Power = F*d/t = mg*d/t
=(60*10)*1.2/1.5 = 480 J/s = 480 Watts.
To determine the power expended by the weightlifter, we can use the formula:
Power = Work / Time
To calculate the work done by the weightlifter, we need to find the force exerted and the distance covered.
1. Calculate the force exerted:
Newton's second law states that the force (F) required to accelerate an object is given by the formula:
F = m * a
Where m is the mass of the object and a is the acceleration. In this case, the weightlifter is lifting the barbell vertically against gravity, so the acceleration is equal to the acceleration due to gravity (9.8 m/s^2).
F = 60 kg * 9.8 m/s^2
F = 588 N
2. Calculate the work done:
The work done (W) is given by the formula:
W = F * d
Where F is the force exerted and d is the distance covered. In this case, the weightlifter is lifting the barbell vertically, so the distance covered is equal to the vertical distance lifted (1.2 m).
W = 588 N * 1.2 m
W = 705.6 J (Joules)
3. Calculate the power:
Now that we have the work done, we can calculate the power by dividing the work by the time interval:
Power = 705.6 J / 1.5 s
Power = 470.4 W (Watts)
Therefore, the weightlifter expends 470.4 W of power when lifting the 60-kg barbell a vertical distance of 1.2 m in a time interval of 1.5 s.