A 34.8 kg runner has a kinetic energy of 1.09 x 10³ J. What is the speed of the runner?
1 answer:
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The gravitational force on the woman is A) 500 N
Explanation:
There are two forces acting on the woman during her fall:
- The force of gravity,
, acting downward
- The air resistance,
, acting upward
According to Newton's second law, the net force acting on the woman is equal to the product between the woman's mass and her acceleration:
where m is the mass of the woman and a her acceleration.
The net force can be written as
Also, we know that the woman falls at a constant velocity (5 m/s), this means that her acceleration is zero:
Combining the equations together, we get:
which means that the magnitude of the gravitational force is equal to the magnitude of the air resistance:
Learn more about forces and Newton's second law:
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Since energy cannot be created nor destroyed, the change in energy of the electron must be equal to the energy of the emitted photon.
The energy of the emitted photon is given by:
where
h is the Planck constant
f is the photon frequency
Substituting
, we find
This is the energy given to the emitted photon; it means this is also equal to the energy lost by the electron in the transition, so the variation of energy of the electron will have a negative sign (because the electron is losing energy by decaying from an excited state, with higher energy, to the ground state, with lower energy)
The energy of the emitted photon is given by:
where
h is the Planck constant
f is the photon frequency
Substituting
This is the energy given to the emitted photon; it means this is also equal to the energy lost by the electron in the transition, so the variation of energy of the electron will have a negative sign (because the electron is losing energy by decaying from an excited state, with higher energy, to the ground state, with lower energy)