Which conversion is the function of a photovoltaic cell? A) sunlight to mechanical energy B) electricity to heat C) sunlight to
1 answer:
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We can use the law of conservation of energy to solve the problem.
The total mechanical energy of the system at any moment of the motion is:
where U is the potential energy and K the kinetic energy.
At the beginning of the motion, the ball starts from the ground so its altitude is h=0 and therefore its potential energy U is zero. So, the mechanical energy is just kinetic energy:
When the ball reaches the maximum altitude of its flight, it starts to go down again, so its speed at that moment is zero: v=0. So, its kinetic energy at the top is zero. So the total mechanical energy is just potential energy:
But the mechanical energy must be conserved, Ef=Ei, so we have
and so, the potential energy at the top of the flight is
The total mechanical energy of the system at any moment of the motion is:
where U is the potential energy and K the kinetic energy.
At the beginning of the motion, the ball starts from the ground so its altitude is h=0 and therefore its potential energy U is zero. So, the mechanical energy is just kinetic energy:
When the ball reaches the maximum altitude of its flight, it starts to go down again, so its speed at that moment is zero: v=0. So, its kinetic energy at the top is zero. So the total mechanical energy is just potential energy:
But the mechanical energy must be conserved, Ef=Ei, so we have
and so, the potential energy at the top of the flight is
Both require time, but velocity requires displacement and speed requires distance.
Explanation:
Speed and velocity are two different quantities. In fact:
- Speed is a scalar quantity, which gives a measure of how fast an object is moving, regardless of its direction. Therefore, it only has a magnitude, which is given by the ratio between distance covered and time taken:
Therefore, speed does not take into account the direction of motion.
- Velocity, on the other hand, is a vector quantity, so it has magnitude and a direction.
The magnitude of the velocity is given by
where displacement is a vector connecting the initial point with the final point of motion of an object.
The direction of the velocity corresponds to the direction of the displacement.
It must be noted also that in certain situations, the average velocity is zero, while the speed is not zero: for example, for an object completing a circle in a certain time interval, its speed is not zero, while its velocity is zero (because the object returns to the starting point, so the displacement is zero.
Therefore, the correct answer is
Both require time, but velocity requires displacement and speed requires distance.
Learn more about speed and velocity:
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