Riddle Me This 5: Luck And Intuition Play The Cards

This is the first of a series of 3 sets of flipping riddles, which will get progressively harder. Answers can be found below each question, but feel free to ask for hints or let me know if you have the solution! Enjoy! :D

Easier:
I have 5 cards on a table, showing L, 1, F, E, 8 face-up. How many cards do you need to flip to test the rule "If there is a consonant on one side of a card, there is an odd number on the other side"? Which ones?

You definitely need to check the consonant cards, L and F. If they don't have an odd number on the other side, the rule is definitely broken. Now, which do you need to flip, the 1 or the 8? Suppose the 1 was flipped, and there was an A on the other side. That wouldn't actually invalidate the rule! Instead, it is the 8 that should be flipped to make sure that there is a vowel on the other side. In total, then, you need to flip 3 cards--the L, F, and 8.

Harder:
There is a standard deck of 52 playing cards lying face-down on a table. How many do you have to flip to guarantee a straight somewhere (eg. 4, 5, 6, 7, 8)? How about a straight flush (same suit as well)?

Without 4 and 9 (or 5 and 10), no sequences of 5 cards from {1,2,3,4,5,6,7,8,9,10,11,12,13} can be made. That means that you could have picked 11 * 4 = 44 cards without having picked a 4 or a 9, and thus without having made a straight, or a straight flush.