The final velocity of the two pucks is -5 m/s
Explanation:
We can solve the problem by using the law of conservation of momentum.
In fact, in absence of external force, the total momentum of the two pucks before and after the collision must be conserved - so we can write:

where
is the mass of each puck
is the initial velocity of the 1st puck
is the initial velocity of the 2nd puck
v is the final velocity of the two pucks sticking together
Re-arranging the equation and solving for v, we find:

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The refractive index for glycerine is

, while for air it is

.
When the light travels from a medium with greater refractive index to a medium with lower refractive index, there is a critical angle over which there is no refraction, but all the light is reflected. This critical angle is given by:

where n1 and n2 are the refractive indices of the two mediums. If we susbtitute the refractive index of glycerine and air in the formula, we find the critical angle for this case:
If you mark off a beginning time and ending time on the graph,
then the area under the part of the graph between those limits
is the distance covered during that period of time.
Gamma radiation is composed of the stable form of nuclei and most important Helium Atom is released in this reaction !
gamma radiation is due to fission in which the radioactive substance is bombarded and as a result a stable form of that element is formed and a Helium atom !