Answer:
a
The mass is 
b
The velocity is 
Explanation:
From the question we are told that
The speed of the protons is 
The mass of the protons is 
The speed of the rebounding protons are 
The negative sign shows that it is moving in the opposite direction
Now according to the law of energy conservation mass of one nucleus of the unknown element. is mathematically represented as
Where
is the mass of a single proton
So substituting values


The mass of on proton is 
So 

Now according to the law of linear momentum conservation the speed of the unknown nucleus immediately after such a collision is mathematically evaluated as

Now
because before collision the the nucleus was at rest
So

=> 
Recall that 
So

=> 
substituting values


B is the correct answer.
A is incorrect because energy is neither created nor destroyed.
C is incorrect because kinetic energy would keep the ball rolling, so that would not make sense.
Frequency and period are reciprocals.
(one-overs)
Distance covered by the squirrel to look for an acorn :
d = ( 3 m/s ) × 10 s = 30 m.
Time taken to eat an Acron is 5 seconds.
Time taken to cover distance of 30 m with 2 m/s speed is :

Therefore, total time take to get back to where he started is ( 10+5+15 ) = 30 s.
Hence, this is the required solution.
Incorrect didn't flow away from pole cause warmer climate I know cause I tried.
Im'ma guess cause didn't correct the answer but says Flowing away from pole was wrong though.
My guess is crashing with warm water. Might be wrong too though...