The frequency of the wave is 
Explanation:
The frequency, the wavelength and the speed of a wave are related by the following equation:

where
c is the speed of the wave
f is the frequency
is the wavelength
For the radio wave in this problem,


Therefore, the frequency is:

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Explanation:
3: the electricity is generated in the permanent magnet
M1*V1 + M2*V2 = M1*V + M2*V.
1400*25 + 1800*20[180+40]=1400*V+1800*V.
Divide both sides by 100:
14*25 + 18*20[220o] = 14V + 18V.
350 + 360[220o] = 32V.
350 - 276-231i = 32V.
74 - 231i = 32V.
242.6[-72.2o] = 32V.
V = 7.6m/s[-72.2o]=7.6m/s[72o] S. of E.
Answer:
1.40 N
Explanation:
The magnitude of the frictional force is given by:

where
is the coefficient of friction
N is the magnitude of the normal reaction
The coefficient of friction for this problem is
. The magnitude of the normal reaction is equal to the combined weight of the boy and the sled, because the surface is horizontal, so

Therefore, the frictional force is
