Rope Swing!

This summer, my cousin Malcolm and I went to California with my parents. My mom and her crew were paddling in the World Sprints races in Sacramento and Malcolm and I had gone with them to check out colleges. Malcolm and I had a lot of time on our hands because we had to hang out at the lake where the races were for an entire week, one day when we were out paddling we found a rope swing and so we spent a lot of time playing on it. We had a waterproof camera, so this is a picture of me on the rope swing. This picture is an example of circular motion. Circular motion is when an object is rotating about an axis that is outside of the object. Although you cannot see it, the end of the rope is connected to a tree branch, so the axis of my motion is the tree branch. When I let go of the rope, I will become a projectile and no longer have circular motion. This picture also shows kinetic and potential energy. At the moment of this picture, I have both KE and PE because I am in motion and I am above the water, which is my reference point. When I let go of the rope and start to fall toward the water, my KE will increase as my PE decreases. Just in this one picture there is so much physics going on! I never stopped to think this summer that something so entertaining and fun would have so much physics involved. 

The Physics of Ice Skating

In February my friends and I went to the ice palace. In this picture we are skating together with our arms linked and playing the game where you spin in a circular motion with the person on the inside as our axis. The person on the outside of the line gets swung around and when they let go they go really fast. When our arms are all linked, we are generally moving in a uniform circular motion with the centripetal force coming from friction. When the person on the outside lets go, they move in a straight line, instead of continuing in a circle, because inertia causes us to resist change in motion and direction. When we whip the outside person around, we are exerting a torque. Torque = force x lever arm. The force comes from our bodies as we use our arms to push the outside person forward and the lever arm is measured from the axis (the inside person) to the force (which comes from the person next to the outside person), they the torque exerted on the outside person will be larger if you have more people in your line, because then the lever arm is longer.