A car in motion has kinetic energy. What happens to the kinetic energy when the car brakes to a stop? The kinetic energy is tran
1 answer:
Answer:
<em>When a moving car brakes to a stop the </em><em>kinetic energy of the car is converted to heat energy. </em>
Explanation:
A moving car has kinetic energy.
It is given by the equation
Where m denotes mass of the car and v denote sits velocity. When the brakes are applied the velocity becomes zero and the car doesn’t possess kinetic energy anymore.
According to law of conservation of energy can neither be created nor be destroyed but can only be transformed from one form to another. On coming to a stop, the kinetic energy of the car gets converted to heat. The friction between the tyre and the road heats up the tyre.
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Answer:
The mass rate of the cooling water required is:
Explanation:
First, write the energy balance for the condensator: The energy that enters to the equipment is the same that goes out from it; consider that there is no heat transfer to the surroundings and kinetic and potential energy changes are despreciable.
Where w refers to the cooling water and s to the steam flow. Reorganizing,
Write the difference of enthalpy for water as Cp (Tout-Tin):
This equation will let us to calculate the mass rate required. Now, let's get the enthalpy and Cp data. The enthalpies can be read from the steam tables (I attach the tables I used). According to that, and
can be calculated as:
.
The Cp of water at 25ºC (which is the expected average temperature for water) is: 4.176 . If the average temperature is actually different, it won't mean a considerable mistake. Also we know that
, so let's work with the limit case, which is
to calculate the minimum cooling water mass rate required (A higher one will give a lower temperature difference as a result). Finally, replace data: