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All questions of Work, Energy and Power for Class 10 Exam
A car of mass 800 kg slows from 20 m/s to 5 m/s due to brakes. What is the work done by the braking force?- a)-60,000 J
- b)-120,000 J
- c)-150,000 J
- d)-200,000 J
Correct answer is option 'C'. Can you explain this answer?
A car of mass 800 kg slows from 20 m/s to 5 m/s due to brakes. What is the work done by the braking force?
a)
-60,000 J
b)
-120,000 J
c)
-150,000 J
d)
-200,000 J
 | EduRev Class 10 answered |
Work by brakes = change in kinetic energy = 1/2 m (v² - u²)
Substitute: 1/2 × 800 × (5² - 20²) = 400 × (25 - 400)
Calculation: 400 × (-375) = -150,000 J
Conclusion: Brakes do -150,000 J (negative indicates removing energy); magnitude = 150 kJ.
Substitute: 1/2 × 800 × (5² - 20²) = 400 × (25 - 400)
Calculation: 400 × (-375) = -150,000 J
Conclusion: Brakes do -150,000 J (negative indicates removing energy); magnitude = 150 kJ.
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