Answer:
the primary coil current produces a magnetic field, which changes as the current changes. the iron core increases the strength of the magnetic field. the changing magnetic field induces a changing potential difference (voltage) in the secondary coil.
Change in state(from liquid to solid) and change in colour I believe.
Answer:

Explanation:
Given:
height above which the rock is thrown up, 
initial velocity of projection, 
let the gravity on the other planet be g'
The time taken by the rock to reach the top height on the exoplanet:
where:
final velocity at the top height = 0 
(-ve sign to indicate that acceleration acts opposite to the velocity)

The time taken by the rock to reach the top height on the earth:



Height reached by the rock above the point of throwing on the exoplanet:

where:
final velocity at the top height = 0 


Height reached by the rock above the point of throwing on the earth:



The time taken by the rock to fall from the highest point to the ground on the exoplanet:
(during falling it falls below the cliff)
here:
initial velocity= 0 



Similarly on earth:

Now the required time difference:


Answer:
Assume that the ball undergoes motion along a straight line. ... F = m A Force = (mass) x (acceleration) The question tells you the mass and the acceleration. All YOU have to do is take the numbers and pluggum into Newton's 2nd law. F = m A = (0.75 kg) (25 m/s²) = (0.75 x 25) kg-m/s² = 18.75 Newtons .
Explanation:
i looked it up ok