speed=frequency*wavelength, so frequency=speed/wavelength. frequency=80*0.2
Frequency = 16 Hz
One thing you should notice. It is kind of weird. Ke has no direction so that fact that it has velocities associated with it does not matter. It becomes a scaler (something measured by amount alone).
General Formula
Ke = 1/2 m v^2
Formula for this problem
Ke = 1/2 m (v2)^2 - 1/2 m (v1)^2
Givens
m = 1200 kg
v2 = 100 km/hr = 100 km/h * [1 hour / 3600 sec] * [1000 m/ 1km] = 27.8 m/s
v1 = 50 km / hr = 13.9 m/s
Substitution and work.
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delta Ke = 1/2 1200 (27.8)^2 - 1/2 1200 (13.9)^2
delta Ke = 463704 - 115926
delta Ke = 34778 Joules
delta Ke = 34.8 kJ
The change is 34.8 kJ which means that the vehicle gains 34.8 kJ
Explanation:
The total resistance Rt is given by
1/Rt = 1/Ra + 1/Rb + 1/Rc = 1/5 + 1/4 + 1/7 = 0.593
or Rt = 1.69 ohms
The total current I running through the circuit is
I = V/Rt = 2.37 A
The answer is solar flare ; an eruption of high - energy radiation from the sun.