"Homemade" questions on introductory physics

Pinu7

Have you ever thought of the PERFECT question in introductory physics? Stop lying, you know you did.
Let this thread be a collection of original introductory physics questions made by PFers to be used in the classroom.
Note: While at an introductory level it must CHALLENGING and/or interesting.

Format:
Subject(i.e. the chapter this would belong to in your imaginary physics text in your head )
Question
Answer(not full solution, just the short answer w/o explanation)


My question:

Subject: Kinematics

Question: A block is connected to a spring. Its equation of motion is
x(t)=Acos(ft)
where
A=3 meters
f=3(1/sec)
Find the average speed for the interval
0<t<10 sec

Answer: 5.75 meters/second