2. Scientists claim that the ocean floor has magnetic pattems. Why does this support the theory of plate tectonics? A. Magnetic patterns are symmetrical on each side of the mid-ocean ridge, which would indicate that the seafloor is spreading apart like the tectonic plate theory claims.
B. Magnetic patterns can only form after billions of years; this proves that the seafloor has not moved recently, which is what the tectonic plate theory claims. C. Magnetic patterns only form where two plates are moving together, which could be expected if the earth's crust is moving

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?