General Science - Physics (Basics)
SSC CGL 2024: A machine does 2000 Joules of work in 4 seconds. If the efficiency of the machine is 50%, what is the power input to the machine?
SSC CGL 2024: A machine does 2000 Joules of work in 4 seconds. If the efficiency of the machine is 50%, what is the power input to the machine?
hard Q9 of 15
Step-by-Step Solution
Step 1: Understand power and efficiency
Power output = Work done / Time; Efficiency = (Power output / Power input) × 100%.Step 2: Calculate power output
Work done = 2000 Joules, Time = 4 seconds.
Power output = 2000 / 4 = 500 Watts.Step 3: Calculate power input
Efficiency = 50% = (Power output / Power input) × 100.
Power input = Power output / (Efficiency / 100) = 500 / 0.5 = 1000 Watts.Step 4: Recheck options
1000 Watts is 1000 Watts, but check carefully.Step 5: Correction
Recalculate: Power output = 2000 / 4 = 500 Watts.
Power input = 500 / 0.5 = 1000 Watts.Final Answer:
1000 Watts → Option DQuick Check:
Power input = Power output / Efficiency fraction = 1000 Watts ✅
Quick Trick: Power input = Power output ÷ (Efficiency/100).
Common Mistakes:
MISTAKES- Confusing power input with output or ignoring efficiency.
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