This animation walks through worked exam-style problems involving cranes and elevators lifting loads at constant speed. It shows how to calculate work done against gravity using W = mgh, then compute mechanical power as work divided by time, cross-checking with P = Fv. A final comparison of two elevators lifting the same load in different times highlights how power, not work, distinguishes machine performance. Useful for students preparing for physics exams on work, energy, and power.
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Scene 8: Exam Question & Advanced Exercises (Problems 6, 7, & 8)Problem 6 (Exam Style Question - Crane Lifting Load):Prompt & Motion: A small crane lifting a 600 kg load vertically 8.0 m at constant speed in 16 seconds ($g = 9.8\text{ m/s}^2$). Voiceover & Step-by-Step Breakdown:Work Done ($W$): $W = 600 \times 9.8 \times 8.0 = \mathbf{47,040\text{ J}}$ ($47.04\text{ kJ}$). Mechanical Power ($P$): $P = 47,040 / 16 = \mathbf{2,940\text{ W}}$ ($2.94\text{ kW}$). Problem 7 (Exercise 1 - Goods Elevator):Prompt & Motion: Goods elevator of mass $1.5 \times 10^3\text{ kg}$ rising 18 m at constant speed in 30 seconds.Voiceover & Step-by-Step Breakdown:(A) Work Done: $W = 1500 \times 9.8 \times 18 = \mathbf{264,600\text{ J}}$ ($264.6\text{ kJ}$).(B) Power Output (kW): $P = 264,600 / 30 = \mathbf{8,820\text{ W}}$ ($8.82\text{ kW}$).(C) Constant Speed ($v$): $v = 18 / 30 = \mathbf{0.60\text{ m/s}}$.(D) Check using $P = Fv$: $P = (1500 \times 9.8) \times 0.60 = \mathbf{8,820\text{ W}}$ ($8.82\text{ kW}$).Problem 8 (Exercise 2 - Elevators A & B Comparison):Prompt & Motion: Two elevators A and B lift a 600 kg load to the same height (9.0 m). Elevator A takes 24 s, Elevator B takes 12 s.Voiceover & Step-by-Step Breakdown:(A) Useful Work: Equal for both since mass and height are identical: $W = 600 \times 9.8 \times 9.0 = \mathbf{52,920\text{ J}}$.(B) Power Output:Elevator A: $P_A = 52,920 / 24 = \mathbf{2,205\text{ W}}$ ($2.21\text{ kW}$).Elevator B: $P_B = 52,920 / 12 = \mathbf{4,410\text{ W}}$ ($4.41\text{ kW}$).(C) Power Ratio ($P_A / P_B$): $2,205 / 4,410 = \mathbf{0.5}$ (Elevator A takes double the time, so its power is half). IMPORTANT LANGUAGE RULE: All on-screen text must be in Arabic EXCEPT mathematical equations, formulas, laws, symbols, variables, and numerical expressions. Keep every equation, formula, and law exactly as provided, without translating or changing it. Translate only the explanatory text, headings, labels, and descriptions into Arabic. Arabic text must use proper RTL direction and correct Arabic typography. Do not use English text anywhere else on the screen. Audience: student