Roxanne is an expert at blowing bubbles with bubble gum. She discovered that her bubbles were bigger if she stood facing the Sun when she blew them. At lunch she told her three best friends about her discovery and after school they all tried it. No one else was able to blow bigger bubbles when they faced toward the Sun. Which of the following would be best for Roxanne to do next? A. She should prove she is right by blowing bubbles while her friends are watching. B. She should give them each bigger pieces of bubble gum and try it one more time.
C. She should think about what else she is doing that might have made the bubbles bigger.
D. She should ask her friends to try it again and concentrate harder when they face the Sun.

Amass m = 74 kg slides on a frictionless track that has a drop, followed by a loop-the-loop with radius r = 18.4 m and finally a flat straight section at the same height as the center of the loop (18.4 m off the ground). since the mass would not make it around the loop if released from the height of the top of the loop (do you know why? ) it must be released above the top of the loop-the-loop height. (assume the mass never leaves the smooth track at any point on its path.) 1. what is the minimum speed the block must have at the top of the loop to make it around the loop-the-loop without leaving the track? 2. what height above the ground must the mass begin to make it around the loop-the-loop? 3. if the mass has just enough speed to make it around the loop without leaving the track, what will its speed be at the bottom of the loop? 4. if the mass has just enough speed to make it around the loop without leaving the track, what is its speed at the final flat level (18.4 m off the ground)? 5. now a spring with spring constant k = 15600 n/m is used on the final flat surface to stop the mass. how far does the spring compress?