stamen, they produce pollen to fertilize ovaries
Those are called Newton's cradle or Newton's balls.
because they are
hibiscus
There are a number of names for the balls - generally they are called zorbing balls or OGOs.
balls
It's actually the "antecubital" area or region.
Those giant inflatable balls that you can go inside are called zorbs or human hamster balls. They are typically used for fun activities like rolling down hills or across water.
Personally I love Ernie Balls
The property that separates styrofoam balls is their buoyancy. Styrofoam balls are lightweight and have air trapped inside, making them less dense than water. This causes them to float on the surface of water, separating them from denser materials that sink.
Hitting with flat tennis balls doesn't necessarily hurt your strings all that much, but it definitely hurts your game. They can hurt your strings a little if you are using all of your might to swing into the tennis ball, and because it is flat the ball will flatten out over the strings and cause more areas of the string to become weaker.
The plant that produces little red balls as part of its fruit or flowers is likely a pomegranate tree.
Inside.