Answer:
0.46km
Explanation:
45963cm/100cm=459.63m/1000m=0.45963 or 0.46km
Considering that the book is moving with constant speed, the force applied by Anna must be the same that the friction force:

If we clear the previous equation:
The system is located in the HairyFunyon aka near the floor
Answer:
200 m/s
Explanation:
v = distance / time = 50km/250s = 50000m/250s = 200 m/s
I'll be happy to solve the problem using the information that
you gave in the question, but I have to tell you that this wave
is not infrared light.
If it was a wave of infrared, then its speed would be close
to 300,000,000 m/s, not 6 m/s, and its wavelength would be
less than 0.001 meter, not 12 meters.
For the wave you described . . .
Frequency = (speed) / (wavelength)
= (6 m/s) / (12 m)
= 0.5 / sec
= 0.5 Hz .
(If it were an infrared wave, then its frequency would be
greater than 300,000,000,000 Hz.)