I. Inertia- driving away without your sunscreen
When you go to the beach, you have to wear sunscreen to protect yourself from harmful UV rays. Say you are in your driveway packing up to go to the beach, and you put a bottle of sunscreen on the hood of your car. If you forget that it is there, and drive away with it still on your hood, it is going to fall to the ground and you will get burnt at the beach. This is because of Newton’s First Law, which states that objects in motion stay in motion and objects at rest stay at rest unless an unbalanced force acts upon them. Essentially, objects will keep doing whatever they are already doing because they are “lazy” if you will. When the car and sunscreen are parked, they are both at rest. However when the cars starts to move, it is in motion while the lotion stays at rest, because it wants to keep doing what it was previously doing. The car pulled out from under the lotion, and gravity pulled the lotion to the ground.
II. Throwing beach volleyball (free fall)
Playing volleyball on the beach can be fun. When you throw a ball up in the air and it slows and begins falling down towards earth, it is in free fall. Free fall is when objects fall due to the acceleration of gravity. All falling objects fall at a rate of 9.8 meters per second squared. Check out this diagram to see the path, including velocities the ball traveled at certain times during its flight.
When you get to the beach, playing reggae music really helps to set the mood. But to play music, you must have a set of speakers. Speakers work through electromagnetic induction, which is a method of inducing a voltage and current to create sound. In a set of speakers, there is a magnet and a series of wire coils. The interaction between the wire and magnet change the magnetic field of the system, which induces a voltage and then induce a current. The current acts as a signal which moves a cone within the speaker, which produces sound so you can listen to reggae music at the beach!
Here’s a great reggae band I'm into right now...
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IV. Fishing: you pull fish, fish pulls you (Newton’s Third Law)
When I was little, I used to fish with my dad on the shore, and sometimes I would reel in really heavy fish. When you have a big fish on the line, you would assume that the fish is pulling you with a stronger force than you are pulling it because you can literally feel it moving you. However, this assumption is incorrect. Newton’s Third Law states that every action has an equal and opposite reaction. Though it may be hard to believe, you are exerting an equal force on the fish as the fish is exerting on you. The reason why you can feel the fish physically pulling and moving you is because you are experiencing a greater acceleration. This can be explained by Newton’s Second Law, which states that mass is inversely proportional to acceleration, and force is directly proportional to acceleration.
V. Why does the fish pull so hard??
Newton’s Second Law a=f/m
Since the forces of the fish and you are the same, this means that the acceleration and mass are inversely proportional. Since the fish has a smaller mass than you, it will have a larger acceleration than you. And similarly, since you have a larger mass than the fish, you will have a larger acceleration than it does. This larger acceleration will cause you to move.
VI. UV Rays
Golly gee! Since you forgot about your sunscreen on the hood of the car, you are starting to get a little pink. UV rays are harmful ultraviolet light that enter earth’s atmosphere and can be very damaging to your skin. In order for a force to be felt, charges have to be moving perpendicular to the earth’s magnetic field. This means that in theory, you can feel slightly more UV rays at the poles than at the equator. When you are at the poles of the earth, charges are moving parallel to the earth’s magnetic field. Since no force is felt, UV rays can enter the earth’s atmosphere easier than at the equator, where charges move perpendicular and the force keeps them out better.
VII. Motors and boats
Boating is one of my favorite activities during the summer. But a motorboat would never work without a motor. All motors operate upon the same principle, that consists of a current carrying wire and a magnet. When a current runs through the wire, a force is felt from the magnetic field, and causes a torque and the motor runs. Remember that a torque is basically a factor that causes an object to rotate, so when the motor rotates, this causes the propeller to spin, which moves the water and makes the boat run.
VIII. Beach ball vs. bocce ball
Playing bocce ball or throwing around a beach ball is another fun past time at the beach. If you tried rolling a bocce ball and a beach ball at the same time, you will notice that the bocce ball rolls faster than the beach ball. This seems misleading though, because the beach ball is so hollow and light, whereas the bocce ball is so heavy. The reason the bocce ball rolls faster is because its mass is positioned at the axis of rotation (middle), so it has less rotational inertia. The beach ball has more rotational inertia because its mass is located far from the axis of rotation.
IX. Tides
Depending on the time of day when you are at the beach, you will notice that the water starts receding out towards the horizon, or it might come closer into shore. These changes in water levels are called tides. When the moon exerts force on the earth, uneven amounts of force are created on opposite sides of the earth. The side of the earth that is closer to the moon has a larger force, and the side farther from the earth is less affected by the moon’s gravitational force. These opposite forces create a “bulge” around the earth, which creates the tides. Over a period of 24 hours, there are four tides. Two high tides lasting six hours each, and two low tides lasting six hours each. The tides can affect what you do at the beach, because at extreme high tides there is sometimes no sand left to stand on.
X. Lighting
I think it’s funny when it starts raining at the beach, then people run out from the water, as if they weren’t already wet. Anyways…
Sometimes when you go to the beach in the summer, it will start to thunder and lightning. During a lightning storm, the clouds in the sky become negatively charged through friction. The negative charges in the sky induce positive charges in the ground. Since opposite charges attract, the positive charges creep up through the sky towards the clouds and if the circuit is complete, energy rushes up from the ground into the clouds. This energy is released in the form of light that produces lightning, sound that is the sound of thunder, and heat. So next time you go to the beach, think about all the physics involved
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