ANOTHER RUNNING DOG
Explanation:
In the given question it is to find a suitable reference point to describe the motion of dog. Here I could suggest that it is better to compare the dog with another running dog to create the relative speed difference to get a reliable motion variation.
Because the motion of dog is in the linear with respect to the another dog and to the acceleration produced by the dog in the required interval is easy to calculate with respect to another dog which is already in motion.
Hence, I suggest that Motion of dog can be analysed better by analyse the motion variation of dog with another dog running.
d=? v=2.5 u=0 and t=5 therefore the formula to be used to find the distance my brother covered is d=1/2(v-u)t
d=1/2(2.5-0)5
=6.15m
Answer: 
beta particles
Explanation:
Given mass = 14.0 g
Molar mass = 137 g/mol
According to avogadro's law, 1 mole of every substance weighs equal to its molecular mass and contains avogadro's number 
of particles.
1 mole of cesium contains atoms =
0.102 moles of cesium contains atoms = 
The relation of atoms with time for radioactivbe decay is:
Where 
=atoms left undecayed
= initial atoms
t = time taken for decay = 3 minutes
= half life = 30.0 years = 
minutes
The fraction that decays : 
Amount of particles that decay is = 
Thus beta particles are emitted by a 14.0-g sample of cesium-137 in three minutes.
E = mc^2
m = e/c^2
m = 2.7*10^16/(300000^2)
m = 300000
Average speed is worked out from dividing distance by time.
