Top Ten Real Life Examples of Physics Concepts

After a long year, and a lot of learning this is the ranking of my top ten real life examples for physics concepts.

1.Crumpled vs Flat sheet of paper:

Both sheet's of paper are falling with air resistance, therefore they want to reach terminal velocity (f air = f - weight). There are two ways you can increase your f air: increasing surface area or increasing speed. The sheets of paper have the same weight, so they need the same f air to reach terminal velocity. The flat sheet of paper has more surface area, therefore it does not need to speed up to gain more f air. The crumpled piece of paper does not have the surface area needed to reach the f air needed, therefore it will speed up in order to reach increase the f air.

2. Balloon that sticks to the wall:

When someone rubs the balloon in someone's head the balloon picks up electrons from the hair and becomes negatively charged (by friction). After that, the balloon is placed against the wall. Because the wall is an insulator the electrons of the balloon will not be stolen by the wall, but the charges will rearrange in a way that the positive charges will move close to the negatively charged balloon, and the negative charges of the wall will move as far away from it as possible. This process of rearrangement of charges is called polarization.. You might be wondering why it sticks if there is also a force of repulsion between the like charges of the balloon and wall. Here is when Coulomb's law comes in handy! Coulomb's law says that distance is inversely proportional to force so since the opposite charges are closer together, the force of attraction is stronger than the force of repulsion, therefore the balloon sticks to the wall!

3. Roller Coasters:

Roller coasters work due to conservation of energy. The first hill is always the highest one so that it accumulates enough energy to go through all the elevations. As the car goes down, the PE goes down but KE goes up. If added together at any part of the ride, the KE and PE of the car will equal the PE that the car had on the first hill.

4. Balancing a see-saw:

If you have too people with different weights it is impossible to maintain the board balanced if they are both sited the same distance from the axis of rotation since for a system to be balanced there needs to be equal torques. To make the board balanced with different weights you need to increase the lever arm (lever arm = smallest distance from the axis of rotation, always perpendicular to force) of the person with the least weight so that the torques equal. In practice the heaviest person of a see-saw needs to sit close to the center while the lightest one sits away from it.

5. Fouette Turns

A ballerina turning is an example of conservation of angular momentum. The girl extends her leg and arms and that increases her rotational inertia (because her mass is farther away from the axis of rotation) and therefore decreases her rotational velocity since angular momentum is conserved.

6. Bouncing Ball vs. solid ball - Which can knock a block over?

The answer to that question is the bouncing ball! The reason why the bouncing ball knocks the block over is because there is not only one force acting on that block. Because of Newton's third law, we know that for every action there is an equal and opposite direction therefore ball pushes block, block pushes ball in both cases. The bouncing ball not only causes that force, the ball will bounce on the block adding another force that causes the block to fall over.

7. How to find out the height of a building
Go to the top of the building drop a ball from the top of it and record how long it took to reach the ground. Do this a few times plug in the average time for t in the how far equation (d = 1/2 gt2) and 9.8 for g! Do the math... and now you know how tall the building is!

8. Forgetting something on top of the car and driving away

Have you ever stopped to observed that the object is at the same place it was before but on the ground? This concept is explained by Newton's first law! The object was at rest and therefore wanted to stay at rest, there was no outside force to stop it from doing so therefore the object continued in the same place but on the floor.

9. Best way to break a brick

In the equation J = f Δt , in order to prove that time determines the force necessary to achieve a certain
impulse, the impulse needs to be proven constant. To prove impulse is constant you need to state that
regardless of the time, the hand of the fighter is moving and comes to a stop therefore since the mass is
obviously the same and P = mv, the change in impulse is the same (ΔP = Pfinal - Pinitial). We stated before
that J = ΔP therefore J is constant! To continue to answer the question, you should now state that J is also

J = fΔt. Because of the last equation is possible to afirm that the smallest the time of contact the greater the force will be in order to achieve the constant J. Since to break a brick you need the greatest force possible, the time of contact should be as small as possible.

10. How a credit card works:

A credit card works because it contains magnets placed in a specific pattern. The credit card machine has coil of wires that cause a change in magnetic field when the card is swiped. This process is called electromagnetic induction. The change in magnetic field induces a voltage that creates a current that is used to signal your account information to the machine.