Answer:
D. shortest wavelength
Explanation:
Photons with the highest energy have the shortest wavelength. The shorter the wavelength, the higher the energy of a photon.
A photon is a quantity that transmits electromagnetic energy from one place to the other.
- Gamma rays have photons that transmits the highest amount of energy.
- The rays have the shortest wavelength and highest frequency of all electromagnetic radiations.
Energy, wavelength and frequency of a photon are connected using the expression:
E = h f = 
E is the energy
h is the Planck's constant
f is the frequency.
Given parameters:
Displacement = 8km
Velocity = 3.8km/h
Unknown:
time = ?
Solution:
Velocity is displacement divided by time.
Velocity = 
Displacement = velocity x time
Input the parameters:
8 = 3.8 x time
Time = 
= 2.1s
The time taken is 2.1s
The additional force needed to bring the car into equilibrium is frictional force.
Answer:
So coefficient of kinetic friction will be equal to 0.4081
Explanation:
We have given mass of the block m = 0.5 kg
The spring is compressed by length x = 0.2 m
Spring constant of the sprig k = 100 N/m
Blocks moves a horizontal distance of s = 1 m
Work done in stretching the spring is equal to 
This energy will be equal to kinetic energy of the block
And this kinetic energy must be equal to work done by the frictional force
So 
So coefficient of kinetic friction will be equal to 0.4081
