Let say the two train cars are of masses
and 
now if the speed of two cars are
and 
then we can say that the momentum of two cars before they collide is given by

here two cars are moving in opposite direction so we can say that the net momentum is subtraction of two cars momentum.
Now since in these two car motion there is no external force on them while they collide
So the momentum of two cars are always conserved.
hence we can say that the final momentum of two cars will be same after collision as it is before collision

Solve for "x"
X=force
18/6=x/9
cross multiply
162=6x
x=27
Hope this helps
A plane mirror always forms a virtual image. the image and the object are the same distance from a flat mirror, the image size is the same as the object, and the image is upright!
True.
A contact force is a force between two objects that are physically in contact with each other: an example of a contact force is the normal reaction of a table supporting a book.
A non-contact force is a force between two objects that are not physically in contact with each other: an example of non-contact force is the gravitational attraction between the Earth and the Moon.
The correct option is (D) Gamma (

)
Explanation:Now this question is a tricky one because all of these options are somehow involved in radioactive decay; however, in this case the SYMBOL is required NOT the elements. There are three symbols involved in radioactive decay, which are:
1. α for alpha decay
2. β for beta decay
3. γ for gamma decay
In the options only one symbol is present which is
gamma. Hence option (D) Gamma ( 
) is the correct answer.
-i