Question

Q14: Give reasons
Why the efficiency of heat engine not 100%?
Bigger drops falls faster than smaller drops.
III) Why is it dangerous to stand on the edge of a platform when a train passes by?
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Answer 1

1) Efficiency of a heat engine cannot be 100% because only a part of heat given to the system is recovered as work rest passes on to source. If the engine was an ideal reversible carnot engine the efficiency would be 100%. But a reversible process is an ideal conception.

2) Due to larger force of gravitation acting on them on account of increased mass

3) As the train passes with high velocity the air pressure decreases at our front side if we are standing on edge of train. On contrary air pressure is high on back side. As a consequence we will be pushed towards the train.