Question

LOTS OF POINTS

How much time would it take a crane to unload a railroad car of scrap metal if:

1. The total load of scrap metal weighs 50,000 N
2. The crane must carry the load a distance of 20 meters.
3. The power of the crane is 2,000 Watts.
4. The crane can carry 3,000 N of metal at a time.
5. It takes 30 seconds for the crane to pick up the load, carry it 20 meters, drop it and return to the railroad car.

Please solve and give an explanation.

Answer 1

Total F = 50,000N/3,000N at a time = 16.67 trips
d = 20m, t = 30s/trip
P = 2,000W
P = F×d/t, 2000 = 3000×20/30 = 2000 ✔ YES
So over 16.67 trips, rounded up to 17 (because you can't have a fraction of a trip), each trip takes 30s = 30s/trip × 17trips = 510s
510s × 1m/60s = 8.5 mins