Physics today

We had an interesting problem today (3.5 #3).  It involved two inline skaters holding on to a rope.  One skater pulled the rope, hand over hand.  We were given the force that they pulled with, and the distance they were separated, and the mass of each skater, and had to figure out the time it would take them to meet.

After looking at free body diagrams there was still some confusion about what would happen, so we modeled the situation.

We had two classmates on rollerblades pull on a ruler (no rope here today) and noticed that they both moved towards each other.  We knew now that they would meet in the middle.

Here’s the math that we did to show how we figured out the time it would take.  We needed our kinematice equations from last unit to help us out.

It is satisfying to be able to solve tricky problems.