Answer:
Explanation:
Given
mass of box 
coefficient of kinetic friction 
coefficient of Static friction 
cart is moving with constant velocity therefore Net Force is zero
Since there is no net acceleration therefore friction force will be zero
mathematically

where 



Since the current is inversely propotional to its resistance, when the voltage is doubled the current will be one-half
Answer:
D
Explanation:
because two vectors which align in the same line adds one to another
It is the energy of the electrons I believe
If you have a string that is fixed on both ends the amplitude of the oscillation must be zero at the beginning and the end of the string. Take a look at the pictures I have attached. It is clear that our fundamental harmonic will have the wavelength of:

All the higher harmonics are just multiples of the fundamental:

Three longest wavelengths are: