Answer:
e = Δφ / Δt induced emf is proportional to enclosed flux
Also φ = B * A flux is proportional to area and enclosed field
If the induced emf e increases with time than the flux and hence the magnetic field is increasing with time (replace B with G)
Since e = ΔG * A / Δt if e is linear then G must also be linear and be proportional to the time
Explanation:
initial velocity U = 20m/s
Final velocity V = 35m/s
time = 15.0 secs
change in velocity = 35 - 15
= 20m/s
acceleration a = change in velocity/time V/t
a = (35-20)/15
a= 15/15
Hence, your acceleration is 1m/s^2
Here we can say that there is no external torque on this system
So here we can say that angular momentum is conserved
so here we will have

now we have



similarly let the final distance is "r"
so now we have


now from above equation we have


so final distance is 0.04 m between them