The Top 10 of Physics

The Top 10 Uses of Physics During the Summer

1)             Let’s say it’s a regular summer day and you are planning to go to the beach (and you live near the beach).  So, you wake up and make a smoothie for breakfast. This smoothie would not be a possibility without physics! There is a motor in the blender, which allows the blender to work. How does this motor work?

Electrical energy is converted to mechanical energy. A current carrying wire feels a fore in a magnetic field. That is the underlying principle. Then, the force the loop feels will cause a torque. This torque will cause a spin and will cause the blender to rotate.

           

2)             While drinking your smoothie, you turn on the television.  Even this simple gesture involves physics. All houses are wired in a parallel circuit. A parallel circuit has electrical devices connected to the same two points. The pathway for current from one end of the battery to the other is completed if only one device is running rather than all the devices in the circuit.  The more appliances added to the circuit the resistance decreases, the current increases, the brightness remains constant and when one device isn’t working or being the used the rest are not affected. Households use parallel circuits because it is more efficient. Parallel circuits allow households to run multiple devices without running other devices unlike series where it is all or nothing. This is why you can turn the television on without turning on the rest of the devices in the house. The only major disadvantage to parallel circuits is the heat factor. The more current and less resistance there is (which happens the more devices are on), there is high heat, which could potentially turn into a fire. A fuse/circuit breaker prevents this from happening. A fuse is used to prevent the current from getting to this dangerous level. The fuse melts and snaps turning the circuit off. A fuse is used in parallel circuits but it is set up in series.

3)             If you are planning on going to the beach, it would be wise to check the tides before you went. Tides are caused by the difference in force felt by the opposite sides of the earth. Whichever side is closer to the moon will feel the greater force. There are two high tides and two low tides each day (4 tides per day total). High to low tide has a time span of 6 hours and from high tide to high tide and low tide to low tide there is a time span of twelve hours. There is not a specific time each day at which these tides occur. It’s constantly changing because the moon is constantly orbiting the earth. It takes about 27 days for the moon to complete a full orbit. There is a tidal bulge that forms around the earth.

There are two tides we learned about called neap tides and spring tides. During spring tides the moon is either a full moon or a new moon and the tides are at its highest highs and lowest lows. Hurricane Sandy was so destructive because it came at a full moon therefore it was a spring tide so the tides were at its most extreme. If Hurricane Sandy had come during a neap tide or a half moon, the damage would have been much less severe. This is because during neap tides, the high tides aren’t as high as usual and they aren’t as low as usual. Here are images of each to show the position of the earth, moon, and sun during each of these tides.

To the left is an image of spring tides. There are two moons in this picture two show that the moon can either be to the left or right of the earth during spring tides. Also notice the tidal bulge is directed towards wherever the moon is.  The high tides will be where you see the tidal bulge and the low tides will be above and below the earth.

To the right is an image of neap tides. Again there are TWO moons in this picture to show that the moon can either be directly above or below the earth during neap tides. Also notice the tidal bulge is directed towards wherever the moon is.  The high tides will be where you see the tidal bulge and the low tides will be to the left and right of the earth. (High tides and low tides occur on opposite sides of the earth.)

An important note to keep in mind when thinking about tides is that lakes don’t experience tides. Lakes don’t experience tides like the ocean does because the mass of the lake is not nearly big enough to be affected by the pull of the moon.  

So, before going to the beach, it is key to know whether it will be high tide or low tide because it is constantly changing.

4)              You decide to pack a lunch for the beach. So, you cut up watermelon to put in a ceramic bowl and put plastic wrap to cover the watermelon. This plastic wrap doesn’t just magically stick to the bowl.  Thanks to physics we know why exactly, the plastic wrap sticks to the bowl. The plastic wrap is charged by friction and when brought near the bowl, the bowl polarizes. The positive charges in the bowl move close to the negative plastic wrap and the negative charges in the bowl move away from the plastic wrap. The distance between the opposite attractive chargers is smaller than the distance between the like repelling charges. Coulomb’s law states that the force between any two charges are inversely proportional to the distance. F=kq1q2/d^2. Because there is a greater distance between the repulsive forces, the forces between them will be less than closer attractive forces. Therefore, the plastic sticks to the ceramic bowl. [INSERT IMAGE]

5)              Finally you’re on the road to the beach. You are talking to your friend and realize there is a stop sign. You stop suddenly because you weren’t paying close enough attention. Luckily, all cars have headrests and seatbelts. When the car is moving, everything else in the car is also moving. If the car comes to an abrupt stop, everything keeps moving that is not attached to the car. We know this because according to Newton’s First Law, when an object is in motion it will want to stay in motion unless a force is acted upon it. Therefore, your head and your body will want to keep moving forward. The seatbelt prevents your body from continuing forward through the car. Your head pulls backward naturally and would continue moving backwards, however the headrest acts as a force to prevent your head from continuing backwards. Thanks to car designers knowledge on physics and Newton’s First Law of Motion, you’re safe and are able to continue on to the beach.

6)              You continue on your way and approach a stoplight. How does this stoplight work? Well, physics makes this answer simple. In the pavement, there is a loop of wire. When the car, which is magnetic, moves over the wire, it changes the magnetic field of the loop. This change induces voltage, which causes a current. [Mechanical energy is converted to electrical energy.]This current is a signal to the stoplight to change allowing you to continue on to the beach.

7)              Finally you get to the beach, you carry the lunch cooler to the beach. Although this may feel challenging and it may feel like you are doing a lot of work, however, in physics terms, you are actually doing NO work. The force, which is the cooler, being pulled down by gravity is not parallel to the horizontal distance the cooler is moving. Work is the effort exerted on something that will change its energy. Work equals force times distance. [Work=Force X Distance] Work is measured in Joules. The force and distance must be parallel to one another in order for there to be work done.

8)              You and your friends decide to race on the beach. The fundamentals of running comes from physics too. All runners bend their legs when they run because they are moving their legs closer to their axis of rotation (their hips). We know this is important from the property of rotational inertia. Rotational inertia is the property of an object to resist changes in spin or rotation. It is not based upon the mass of an object, rather where that mass is located or how it is distributed (how far it is from the axis of rotation). Therefore, runners bring their mass closer to the axis of rotation to lower their rotational inertia. The farther away from the axis of rotation, the higher rotational inertia an object has.

9)              After a long day at the beach, the typical summer afternoon storms rolls in. What causes lightning? Lightning is a good example of induction. Charging by induction takes place during thunderstorms. The clouds are negatively charged by friction and the clouds positively induce the ground.  The attractive forces eventually become strong enough to produce lightning. Therefore lightning starts from the ground, travels upward and then recedes toward the ground. (Click on image for a closer view.)

10)           On your way back into town, you decide to drive through downtown (Beaufort), the storm hasn’t reached downtown yet and people are walking on the streets and horses are pulling buggies filled with tourists. How can a horse possibly do this? The reason the horse pulls a buggy is because of a few things. We know the horse exerts the same force on the buggy that the buggy exerts on the horse because of Newton’s Third Law which states that every action has an equal and opposite reaction. But the reason the horse and the buggy move forward is because the horse pushes on the ground with a greater force than the buggy pushes on the ground. A key part of this drawing is that the pink arrows are larger than the grey arrows to show that the horse has a greater force than the buggy. So here are the action reaction pairs; the grey would be buggy pushes on earth forward and earth pushes on buggy backward. The orange would be, the horse pulls buggy forward and the buggy pulls the horse backward. Lastly, the pink would be the horse pushes on the earth forward and the earth pushes on the horse backward. Therefore, the horse is able to pull the buggy forward.