Chapter 7
Work, Energy, and Simple Machines
CBSE Class 9
Science Solutions
Educart Science class Class 9 NCERT Exemplar cover
Question:

Is it possible to build a perpetual motion machine, which once started, could continue doing useful work forever, without any fuel or electricity? [Pg. No. 135]

Answer: Verified

No, a perpetual motion machine is not possible. This is because it would violate the Law of Conservation of Energy, which states that energy cannot be created or destroyed, only converted from one form to another. In any real system, some energy is always lost due to friction, air resistance, heat, or sound. Because of these losses, the machine would gradually slow down and stop unless external energy is supplied. Therefore, a device that runs forever and does useful work without any energy input is impossible according to the laws of physics.

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More NCERT Questions
Explain why roads on hills are built to wind around in gentle slopes rather than going straight up? [Pg. No. 132] Why is it easier to open the lid of a can by using a spoon as shown in Figure.[Pg. No. 135] To reach a higher floor, we find climbing an inclined ladder easier in comparison to climbing a vertical ladder. Explain why.[Pg. No. 132] State whether True or False. (A) Work is said to be done when a force is applied, even if the object does not move. (B) Lifting a bucket vertically upward results in positive work done on the bucket.