Answer:
friction help to slow motion in other word it oppose motion, but in a frictionless environment object would move with difficult stopping point.
To develop this problem it is necessary to apply the concepts related to the Dopler effect.
The equation is defined by

Where
= Approaching velocities
= Receding velocities
c = Speed of sound
v = Emitter speed
And

Therefore using the values given we can find the velocity through,


Assuming the ratio above, we can use any f_h and f_i with the ratio 2.4 to 1


Therefore the cars goes to 145.3m/s
Answer:
5 mg, 
Explanation:
First of all, let's rewrite the mass in grams using scientific notation.
we have:
m = 0.005 g
To rewrite it in scientific notation, we must count by how many digits we have to move the dot on the right - in this case three. So in scientific notation is

If we want to convert into milligrams, we must remind that
1 g = 1000 mg
So we can use the proportion

and we find
