Answer:
It is impossible to create a perpetual motion machine because some of the energy will always be lost in the conversion and therefore it will eventually stop.
Correct Answer : Option B
Explanation:
The perpetual motion machine is impossible machine as it is hypothetical working machine which would be in motion for an indefinite time in continuity of the motion. The continuity of motion for an indefinite time would mean that the working principle of the machine would never allow the dissipation of energy from the machine and all the machine would ultimately reserve all the energy and be converting it into forms without any loss.
This working principle is violation of first and second laws of thermodynamics and hence a machine will eventually lose some of its energy in every conversion of the working cycle and hence there will be a time where the machine would be stopped, and hence a perpetual motion machine cannot be made.
Is a physical change because only the state of the matter has changed.
Physical changes can often be reversed. Allowing the water to evaporate will return the salt to a solid state.
It has not combined with the water to cause an irreversible chemical reaction.
Answer:
270 mi/h
Explanation:
Given that,
To the south,
v₁ = 300 mi/h, t₁ = 2 h
We can find distance, d₁

To the north,
v₂ = 250 mi/h, d₂ = 750 miles
We can find time, t₂

Now,
Average speed = total distance/total time

Hence, the average speed for the trip is 270 mi/h.