The Metric, and the US Standard systems. :)
X-rays have shorter wavelength than visible light. But that's hardly the reason that they're used for medical imaging. xrays have much higher frequencies then visible light which means they have much greater penetrating ability. with xrays you can see inside the body. you can't do that with a visible flashlight no matter how bright and powerful it is.
An electric generator is when a magnet is rotated through a coil of wire to produce an electric current.
Answer:
Wavelength, 
Explanation:
Given that,
Mass of the particle, 
Acceleration of the particle, 
Time, t = 5 s
It starts from rest, u = 0
The De Broglie wavelength is given by :

v = a × t



Hence, this is the required solution.
Answer:
The mass of the ice block is equal to 70.15 kg
Explanation:
The data for this exercise are as follows:
F=90 N
insignificant friction force
x=13 m
t=4.5 s
m=?
applying the equation of rectilinear motion we have:
x = xo + vot + at^2/2
where xo = initial distance =0
vo=initial velocity = 0
a is the acceleration
therefore the equation is:
x = at^2/2
Clearing a:
a=2x/t^2=(2x13)/(4.5^2)=1.283 m/s^2
we use Newton's second law to calculate the mass of the ice block:
F=ma
m=F/a = 90/1.283=70.15 kg