Answer:

Explanation:
consider the mass of each train car be m
m₁ = m₂ = m₃ = m
speed of the three identical train
u₁ = u₂ = u₃ = 1.8 m/s
m₄ = m u₄ = 4.5 m/s
m₅ = m u₅ = 0 (initial velocity )
final velocity
v₁ = v₂ = v₃ = v₄ = v₅ = v
using conservation of momentum
m₁u₁ + m₂u₂ + m₃u₃ + m₄u₄ + m₅u₅ = m₁v₁ + m₂v₂ + m₃v₃ + m₄v₄ + m₅v₅
m (1.8 + 1.8 + 1.8 +4.5) = 5 m v


The force needed to give a car of mass 800 kg an acceleration of 2.0 ms-² is 1600N.
<h3>How to calculate force?</h3>
The force needed to push an object can be calculated by multiplying the mass of the object by its acceleration as follows:
Force = mass × acceleration
According to this question, a car of mass 800 kg has an acceleration of 2.0 ms−². The force is calculated as follows:
Force = 800kg × 2m/s²
Force = 1600N
Therefore, the force needed to give a car of mass 800 kg an acceleration of 2.0 ms-² is 1600N.
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Astronomers find white dwarfs that distinguish them from main sequence stars because white dwarfs get really hot, we can search for their ultraviolet radiation.
<h3>What is a white dwarf?</h3>
A white dwarf is a very hot star that radiated much energy in the form of ultraviolet radiation.
This UV radiation is initially very bright and then these stars become red with time.
In conclusion, Astronomers find white dwarfs they can search for their ultraviolet radiation.
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Direction. Velocity is a vector that describes both speed and direction, while speed is a scalar that describes only speed regardless of direction.
It depends because it’s might be lolilolololol 21212132