How many photons per second are emitted by the antenna of a microwave oven if its power output is 1.00 kw at a frequency of 2515
1 answer:
The power of the antenna is
and since the power is the emitted energy divided by the time, the energy emitted per second is
The frequency of the emitted photons is
So the energy of a single photon is
Therefore, to find the number of emitted photons per second, we should divide the total energy emitted by the antenna in 1 second by the energy of a single photon:
and since the power is the emitted energy divided by the time, the energy emitted per second is
The frequency of the emitted photons is
So the energy of a single photon is
Therefore, to find the number of emitted photons per second, we should divide the total energy emitted by the antenna in 1 second by the energy of a single photon:
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Answer:
Explanation:
According to Newton's 2nd Law of motion the force is proportional to the mass
and acceleration
:
(1)
On the other hand, the equation for the Centripetal force is:
(2)
Where:
is the velocity
is the radius of the circular motion
Making (1) and (2) equal:
(3)
Hence:
This is the expression for the centripetal acceleration
It should be noted, this acceleration is directed toward the center of the circumference of the circular motion (that's why it's called centripetal acceleration).
a) The work done by the tree is
b) The amount of force applied is 2880 N
Explanation:
a)
According to the work-energy theorem, the work done on the car is equal to the change in kinetic energy of the car. Therefore, we can write:
where
W is the work done on the car
m is the mass of the car
u is its initial speed
v is its final speed
For the car in this problem, we have:
m = 2000 kg
u = 12.0 m/s
v = 0 (since the car comes to a stop, after the crash)
Therefore, the work done by the tree on the car is:
The work is negative because it is done in the direction opposite to the direction of motion of the car.
b)
The work done by the tree on the car can also be rewritten as
where
F is the force applied on the car
d is the displacement of the car during the collision
In this situation, we have:
is the work done
is the displacement of the car during the collision
Solving the equation for F, we find the force exerted by the tree on the car:
Where the negative sign means the force is applied opposite to the direction of motion of the car. Therefore, the magnitude of the force applied is 2880 N.
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Answer:
B. 7.07 m/s
Explanation:
The velocity of the stone when it leaves the circular path is its tangential velocity, , which is given by
where is the angular speed and
is the radius of the circular path.
is given by
where is the frequency of revolution.
Thus
Using values from the question,
<em>Note the conversion of 75 cm to 0.75 m</em>