It will travel slowest through gases.
Answer:
He needs 1.53 seconds to stop the car.
Explanation:
Let the mass of the car is 1500 kg
Speed of the car, v = 20.5 m/s
He will not push the car with a force greater than, 
The impulse delivered to the object is given by the change in momentum as :

So, he needs 1.53 seconds to stop the car. Hence, this is the required solution.
Work needed = 23,520 J
<h3>Further explanation</h3>
Given
height = 12 m
mass = 200 kg
Required
work needed by the crane
Solution
Work is the transfer of energy caused by the force acting on a moving object
Work is the product of force with the displacement of objects.
Can be formulated
W = F x d
W = Work, J, Nm
F = Force, N
d = distance, m
F = m x g
Input the value :
W = mgd
W = 200 kg x 9.8 m/s²x12 m
W = 23520 J
If you know an element’s atomic number, you will learn the number of protons and electrons. The atomic number is equal to the number or protons and electrons. You can also find the number of neutrons, by subtracting the atomic mass from the atomic number.
For example, Fluorine’s atomic number is 9, and its atomic mass is 19. So, the number of electrons and protons in fluorine is 9. The number of neutrons the is equal to 19-9. Thus, Fluorine has 10 neutrons.
Hope this helps :)
Answer: a
Explanation: because i said so