What is the speed of an 800 kg automobile if it has a kinetic energy of 9.00 x 10^J?
1 answer:
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Answer:
Speed = 0.00392 m/s
Explanation:
Solution:
Frequency of the radio = 85 MHz
If we have the frequency, we can calculate the wavelength of the radio wave.
As we know,
Frequency = speed of light/wavelength
wavelength = c/f
c = speed of light = 3 x m/s
So,
Wavelength = 3 x m/s / 85 x
Hz
Wavelength = 3.5294 m
Man gets disturbed reception at t = 15 min
t = 15 x 60 = 900 s
t = 900 s
Speed = distance/time
Here, distance is wavelength. So,
Speed = 3.5294 m / 900 s
Speed = 0.00392 m/s
Hence, the man's car is going with speed of 0.00392 m/s
1. False
Explanation: it's exactly the opposite. In fact, Lenz's law states that the induced current and the induced emf in a conductor are generated in such a direction that opposes to the change in magnetic flux through the coil. This is summarized by the negative sign in the Faraday's Newmann Lenz law:
where is the emf induced and
is the rate of change of magnetic flux through the coil.
Lenz's law is a consequence of the law of conservation of energy. In fact, we have:
- If the magnetic flux through a coil is increasing, then the induced current has a direction such that the magnetic field generated by the coil is opposite to the direction of the external magnetic field, in order to decrease the total flux
- If the magnetic flux through a coil is decreasing, then the induced current has a direction such that the magnetic field generated by the coil is in the same direction as the external field, in order to increase the total flux
2. False
Explanation: the magnetic flux through a surface is given by
where
B is the magnitude of the magnetic field
A is the surface area
is the angle between the direction of B and the normal vector to the surface
As we see, the magnetic flux depends not only on B and A, but also on the orientation of the coil with respect to the magnetic field.
3. False
Explanation:
- Sound waves are mechanical waves: mechanical waves are waves consisting of oscillations of the particles in a medium. Due to their nature, therefore, mechanical waves can propagate only in the presence of a medium
- Electromagnetic waves are NOT mechanical waves: they consist of oscillations of electric and magnetic fields, in a direction perpendicular to the direction of propagation of the wave. Since em waves are not mechanical waves, they do NOT need a medium to propagate, since they can also travel through a vacuum; therefore the original statement is false.