A spinning ice skater will slow down if she extends her arms away from her body. Which of the following statements explains this
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Answer:
We know from the basic speed distance relation that
Since the car started from rest and it covered the distance between the 2 officer's in 19 minutes we have speed of the car
Which clearly exceeds the limit of
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
While plane is moving under tailwind condition it took time "t"
so here we will have
here net speed of the plane will be given as
similarly when it moves under the condition of headwind its net speed is given as
now time taken to cover the distance is 2 hours more
now solving two equations
solving above for v_w we got