Final answer:
The power expended by the weightlifter when lifting a 56-kg barbell a vertical distance of 1.0 m in a time interval of 1.4 s is approximately 392 watts, calculated by dividing the work done (548.8 joules) by the time taken (1.4 seconds).
Step-by-step explanation:
To calculate the power expended by a weightlifter, we need to determine the work done and then divide it by the time taken. The formula to calculate work done (W) in lifting an object is W = mgh, where m is the mass in kilograms, g is the acceleration due to gravity (9.8 m/s2), and h is the height in meters. In this case, the mass (m) is 56 kg, g is 9.8 m/s2, and the height (h) is 1.0 m. Therefore, the work done is:
W = 56 kg × 9.8 m/s2 × 1.0 m = 548.8 J.
Power (P) is the rate of doing work, so P = W / t, where t is the time in seconds. The time taken is 1.4 s, so the power is:
P = 548.8 J / 1.4 s ≈ 392 W (rounded to two significant figures).
Thus, the power expended by the weightlifter is approximately 392 watts.