Balls come in a wide variety if sizes. It would depend on the dimensions and the density of the material. On earth it would be equal to its weight.
A tennis ball weighs 57 grams, a golf ball weighs 46 grams. So there would be 14.87 golf balls to 12 tennis balls.
687 (Earth) days would equal one year on Mars.
A dint in the surface of a pingpong ball can be removed by putting the ball in hot water. The hot water will expand the air inside the ball and push the dint out, restoring the original shape of the ball.As to a hole? A hole would allow the pingpong ball to fill with water.
Mars would have to find more mass if it wanted to equal the Earth's. It has only 11% of Earth's mass.
Earth is roughly twice as large as Mars, so it would take 2 Mars (approx.) to equal Earth.
One year on earth would equal to 365.2422 days
????? I'd call that IMPOSSIBLE. The only time there would be equal amounts of sun on all parts of the earth would be during a solar eclipse, at which time there would be no sunlight reaching anypart of the earth.
There would be no seasons on Earth if the Earth's axis had no tilt because throughout the year the Earth would get an equal amount of sun everywhere.
Why in the name of god would you want them for?