If you are pushing the coin across the table at a constant rate, the friction of the table and the horizontal force of your hand pushing are equal, and the coin itself moves at a constant rate. If you push a coin and let it go, there is no horizontal force keeping the coin going. Friction slows the coin to a stop. In both cases, the gravitational downward pull of Earth is equally but oppositely resisted by the upward push of table on the coin.
A- a hemisphere is one half of earth.
To answer this question, we would need the formula for the kinetic energy which is Kinetic Energy = ½ x m x v^2
Where the following means: m is the mass of the object and v is the velocity
So At 7 m/s: Kinetic Energy = ½ x 5 x 7^2 = 122.5 J is the answer
