Arailroad flatcar of mass 2000 kg rolls to the right at 10 m/s and collides with a flatcar of mass 3000 kg that is rolling to the left at 5 m/s. the flatcars couple together. their speed after the collision is
a 1 m/s
b 2.5 m/s
c 5 m/s
d 7 m/s
e 7.5 m/s
a (1 m/s)

Option A ) 1m/s

Explanation:

For this case, we can consider flatcar going from left to right:

M₁= 2000 Kg

V₁= 10 m/s

And for flatcar going from right to left:

M₂= 3000 Kg

V₂= 5 m/s

We can first consider our reference system as: everything going from left to right will have a positive value, and everything going from right to left will have a negative value

When we have a plastic crash, and both bodies stick together, we can consider linear momentum conservation:

M₁V₁ + M₂V₂ = (M₁ + M₂)Vₓ  where Vₓ= final speed of of both objects that couple together

Then: Vₓ= (M₁V₁ + M₂V₂)/(M₁ + M₂)

We now can replace our above numbers, considering that, for flatcar number 2, we should consider a speed with a negative value, according to our reference system (as it goes from right to left):

Vₓ= (2000Kgx10m/s – 3000Kgx5m/s)/(2000Kg + 3000Kg)

Vₓ= 1 m/s

So both flatcars will remain togheter, with a final speed (Vₓ) of 1 m/s, moving from left to right

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.