Two Lifts, Same Height — One Gets There First
Two lifts stand side by side in the same building. Each carries a 600 kg load to the same floor, 9.0 m up. Lift A takes 24 s; lift B does it in 12 s. People watching the faster one say it "does more work" — and that is the sentence this simulation is built to settle. Press the one button, and instead of watching the cabins, watch the two glowing columns beside the shafts. They are work meters, and they fill at different rates to exactly the same mark.
Cara memakai simulasi ini
- Send them both up — the single button. Both lifts start together and the clock starts with them; press it again once they are both at the top to run the race afresh.
- Drag anywhere on the scene to orbit the cut-away core and look into either shaft.
Yang perlu diamati
- The two work meters stop at the same ring, marked 52.9 kJ, every time. B simply gets there sooner.
- At t = 12 s, B is at the top while A is exactly halfway — and B's meter is exactly twice as full as A's.
- The power readings never change during the ride: 2.2 kW and 4.4 kW are properties of the motors, not of how far along the trip is.
- "The more powerful motor uses less electrical energy" is a salesperson's line, and the meters disprove it: both motors hand the load the same 52.9 kJ. Power is how fast energy moves, never how much.
Fisika di baliknya
Work against gravity is W = mgh. Mass, gravitational field strength, height gained — and no clock anywhere in it. Both lifts raise 600 kg through 9.0 m, so both do 600 × 9.8 × 9.0 = 52 920 J ≈ 52.9 kJ of useful work, every single trip. What separates them is the rate at which that work is delivered, which is the average power P = ΔW / Δt. Lift A: 52 920 / 24 = 2205 W ≈ 2.2 kW. Lift B: 52 920 / 12 = 4410 W ≈ 4.4 kW. The ratio P_B : P_A is 2 : 1, the exact inverse of the ratio of the times. The cabins rise at a constant speed, so the cable force is precisely the weight mg, and each counterweight descends as its cabin climbs.