T=distance over speed
T=40m over 9.8ms
T=answer
Answer: 
Explanation:
Given
Cross-sectional area of wire 
Extension of wire 
Extension in a wire is given by

where, 

for same force, length and material

Divide (i) and (ii)

The color of light that a star emits is somewhat related to its age, whereas the color of light that we actually <em>observe</em> from a star is related to the speed at which it's moving with respect to us.
It is an example of balanced force.
hope this helps. good luck
The initial kinetic energy of the car is

Then, the velocity of the car is decreased by half:

so, the new kinetic energy is

So, the new kinetic energy is 1/4 of the initial kinetic energy of the car. Numerically: