Tides

Having grown up on a peninsula, it is important to know how the tides work. The moon exerts gravitational force on the earth, which creates a difference in force on opposite sides of the earth. Since one side of the earth is closer to the moon (side A), it will have a greater force. And the side furthest away from the moon (side B) is influenced less by gravitational force. These opposing forces create an imaginary “bulge” or “potato” around the earth. Sides A and B with the bulge are at high tide, and C and D at low tide. (Insert diagram here) Spring tides are when high tides are higher than average. These tides occur during a full moon, when the moon sun and earth are all in one straight line. Similarly, neap tides are unusually low tides. These occur during the half moon phase, when the moon and earth are in a line, with the sun across from it. There are four tides every in one full day. Two low tides each lasting 6 hours, and two high tides each lasting 6 hours. Watch this video of the Bay of Fundy, in Nova Scotia Canada, home to the highest tides in the world. Below is this weekend’s tide table for Halls Harbor, Nova Scotia. At 5:18 this morning, the Harbor experienced a high tide of 32.5 feet. At 11:20, the water will leave the harbor, and the low tide will reach a height of 9.8 feet. The current phase of the moon at Halls Harbor is the “Last Quarter”, which means that at this time, the tides will be their average height for this area.

Newton's Third Law meets Platform Nine and Three Quarters

(end 0:08) We are all familiar with the “Platform Nine and Three Quarters” scene from Harry Potter and the Sorcerer’s Stone. Now, lets analyze the physics behind it… When Harry first tries to enter the platform, he hits the brick wall with his cart head on. Which do you think experienced the greater force during the collision; Harry’s cart, or the brick wall? Many people would assume that the brick wall would have more force since it has more mass. However, this is not the case… Newton’s Third Law states that every action has an equal and opposite reaction. That being said, the cart and the platform actually exert equal forces on each other. Which object experiences a greater acceleration? Think back to Newton’s second law… The force is the same, and mass and acceleration are inversely proportional. This means that since the mass of the platform is greater than that of the cart, the acceleration will be smaller. And similarly, since the mass of the cart is smaller, it’s acceleration will be greater. It’s magical, isn’t it?