Usaha vs Daya Kesalahan (Joules vs Watts)
Usaha is energi transferred (joules). Daya is how fast that happens (watts). Ujian punish mixing them.
W = F d · P = W/t · P = F v — 1 W = 1 J/s · convert minutes → seconds
Jebakan 1: Calling daya “usaha” because both use W
Salah: P = 50 W described as “50 joules of usaha.”
Benar: 50 W means 50 joules every second. Usaha would need a time: W = P t.
Perbaikan: Periksa the unit: J → usaha/energi; W (watt) → daya.
Jebakan 2: Leaving time dalam minutes for P = W/t
Salah: 600 J dalam 2 minutes → P = 600/2 = 300 W.
Benar: t = 120 s → P = 600/120 = 5 W.
Perbaikan: Always convert minutes × 60 sebelum membagi for watts.
Jebakan 3: Using P = Fv when gaya is not along kecepatan
Salah: Any F and any v multiplied, even when gaya is perpendicular to motion.
Benar: Gunakan the component of gaya along the kecepatan: P = F v cosθ (or F_parallel × v).
Perbaikan: P = Fv is the special case when gaya and kecepatan are parallel.
Jebakan 4: Mixing mechanical daya with electric P = VI
Salah: A lifting problem answered with P = VI because “daya is VI.”
Benar: Mechanical: P = W/t or P = Fv. Electric circuits: P = VI (or I²R, V²/R).
Perbaikan: Match the rumus to the context — motors can involve both, but the given data tells you which.
Jebakan 5: Same usaha, assuming same daya
Salah: Two lifts of 100 J must both be “the same daya.”
Benar: Same usaha dalam less time means more daya: 100 J dalam 2 s → 50 W; dalam 10 s → 10 W.
Perbaikan: Daya always needs a time (or a kelajuan with gaya).
Kesimpulan
Joules are usaha; watts are joules per second. Ubah time to seconds, and only use P = Fv when gaya lines up with kecepatan.
FAQ
Berapakah the difference between usaha and daya?
Usaha (J) is energi transferred. Daya (W) is the rate of that transfer: P = W/t.
How many watts dalam one horsedaya?
Tentang 746 W for mechanical horsedaya dalam most school conversions.
Latihan W = Fd · Latihan P = W/t · Usaha Kalkulator · Daya Kalkulator · Horsedaya Kalkulator · Daya listrik Kalkulator
W = Fd Rumus Latihan · P = W/t Rumus Latihan · Cara menghitung Usaha · Cara menghitung Daya