Kennedy used the metaphor that this nation has " over the wall of space" to show that Americans will continue to move forward in space exploration no matter how difficult the journey may be.

"Tossed its cap"

Explanation:

He used this phrase because this metaphor to "throw your cap/hat over a wall", means you are committing to doing something. This phrase comes from if you are about to climb over a wall. You would toss your hat over the side of the wall so that it doesn't fall off while you are climbing and it will be waiting for you on the other side once you get down.

But think about it. If you have already tossed your hat over the wall, there is no going back since now it is on the other side and you have to climb over in order to get it back. Kennedy means this because America has already tossed our hat when it comes to space exploration, so there is no going back no matter how hard it gets. :)

active voice: my father cut the tree.

passive voice: the tree was cut by my father.

active voice: people buy newspapers every day.

passive voice: newspapers are bought (by people) every day.

active voice: people have been using movies as political propaganda since world war ii.

passive voice: movies have been used as political propaganda since world war ii.

active voice: donna gave me my birthday present.

passive voice: i was given my birthday present (by donna). / my birthday present was given to me (by donna).

active voice: mom will leave the keys on the counter.

passive voice: the keys will be left (by mom) on the counter.

the words in parentheses are the agent of the passive voice and can be omitted when obvious, generic, or simply unnecessary.