Unit 3 Summary

Newton’s 3rd Law and  Action/Reaction Pairs:

Newton's 3rd law states that: "Every action has an equal and opposite reaction". This means that if someone pushes you are pushing back at him with the same force. If you pull something it will pull you back with the same force. If the earth is pulling you, you are pulling the earth with the same force.

Tug of War / Horse and Cart:

If their was a horse pulling the cart along the street the pull on the rope isn't whats making the cart move with the force, as every action has an equal and opposite reaction, so the net force on the rope is 0 (zero). The horse is able to move the cart because the force he is pushing the ground at is greater than the force the cart is pushing the ground at. So the ground will push the horse forward with an equal and opposite force, the same with the cart. So the equal and opposite force of the horse is greater than the equal and opposite force of the cart, so this is house the horse is able to move the cart.

Forces in Perpendicular directions:

If there was a plain flying to the north direction at 10m/s and the air was blowing at 10m/s to the east. The plain would then be going to the North-east direction as it is the exact midway of both forces, and it has both horizontal and vertical forces acting on it. The plain will also be moving at a speed of 14.1, this is because the plain and the wind form and 10, 10, 10 root 2, triangle.

Gravity and Tides:

Tides are manly caused by the moon than the sun this is because, the moon is closer to the earth. This can be explained by this formula G*(m1m2)/(d^2) this formula if applied shows that the sun has a greater force on the earth than the moon does. But the tides do not depend on the amount of force affecting the sides but the difference of the certain point of the earth from the center of the earth.

Newtons 3rd law

This video in my opinion was very useful as the man in the video shows real life situations in which he asks people questions about the gravitational pull between the earth and the moon, and despite these people knowing Newtons 3rd law (every action has an equal and opposite reaction) they still do not apply it to his questions. They think If an object has a greater mass it will has a larger gravitational pull, but i guess they just didn't fully comprehend Newtons law.

tides

Tide Resource.

 Each day the earth experiences 2 high tides and 2 low tides. They come 1 after the other and last for 6 hours each. For example if at 12am there was a high tide, at 6am there will be a low tide and at 12pm there will be another high tide and at 6pm there will be another low tide.

If a place in the earth is experiencing a high or low tide, the completely opposite side of the world will completely experience the same tide, this is due to the difference of the moons gravitational pull on the earths core. 

The tides have to be equal and opposite, or either the tides will not be able to form.

A spring tide is when the sun and moon are acting on the same sides of the earth and cause higher than normal tides, and a neap tide is where the sun and moon are affecting the earth on perpendicular sides and cause normal tides. 

Unit Summary 2

 

Second Unit Summary

 

 

Free Fall:

 

If a ball was dropped from any height, (neglecting air resistance) the ball will accelerate 10m/s^2 due to gravity, and the equation (d=1/2gt^2) helps you figure out the time it is in the air or the height it was dropped from. So for example if a ball was dropped from an unknown height and it took the ball 3 seconds to hit the ground, how high was it dropped from. d=1/2(10)*(3^2),  d=5*9,  d=45m

 

Projectile motion:

 

If something is thrown off a cliff at an angle (not only downwards but sideways as well) their are two velocities (horizontal / vertical) in affect here. To find exactly where the ball will drop, you first must find the time it is in the air, to do that you have to work on the vertical drop alone. You use the (d=1/2gt^2), then when you get the time, you can also find out the horizontal distance by using this equation (v=d/t) or (d=vt)

For example if you have a cliff that is 80 meters tall and you throw a ball from the top of it with a horizontal velocity of 20m/s where will it land?

d=1/2gt^2,  80=5t^2,  16=t^2, t=4seconds.

Now you can find the horizontal velocity. d=Vt,  d= 20*4, d=80m

 

Throwing things up at an angle:

The time it takes the ball to go up is it exactly the same time it needs to go down, and the ball always accelerates downwards at 10m/s^2. for example if a ball was thrown upwards with a velocity of 30m/s, it would take 6 seconds for it to hit the ground, this is because the first second, it would be moving upwards but has a velocity of 20m/s, the 2nd second the ball will be moving upwards with 10m/s, the 3rd second it would be at the top of it's path with 0m/s, the 4th second it would be going downwards now with 10m/s, the 5th second going downwards with 20m/s, and the sixth second it would hit the ground with 30m/s. 

Newton's 2nd law:

 

"Acceleration is directly proportional to Force and is inversely proportional to mass"

 

If there was a cart that had a string attached on it then to a hook that is playing the role of the force
If the mass of the cart was increasing and the mass of the hook was decreasing, the acceleration of the cart will decrease as mass is inversely proportional to acceleration. But if the mass of the system was kept the same and the mass on the cart was added to the hook, the acceleration would increase, as force is directly proportional to force (a=f/m) (w=mg)

Skydiving:

When jumping off an airplane (with a parachute) the only 2 things affecting your air resistance is the speed that you are travelling at downwards and the surface area you have. When you jump you start the build up speed so that means air resistance also increases which decreases your acceleration downwards. when you hit the first terminal velocity this means that you are going your fastest and that the air resistance it equal to the force of your weight, so your velocity is constant now. As soon as you pull the parachute, the upwards force of air resistance rockets and the weight stays the same, so the acceleration is going upwards, you are still moving downwards but slowing down. after the parachute has been open your force of air resistance slowly decreases as the speed is decreasing, trying to equalize with the weight of the person. When it is equal you hit another terminal velocity, which means that you don't accelerate any more, and the velocity is constant due to the air resistance and the weight being equal. There is one difference between the first terminal velocity and the second, it is that the first is faster (greater velocity) than the second
 

Unit Summary

Unit Summary

-A-

 

In this Units a learnt:

 

1. Net force: The overall forces acting on a object (gravity, weight, friction) and is measured in Newton's. If an object has a netforce of 0N then it is at Equilibrium.

2. Equilibrium: The stage where the net force on the object adds up to 0N, so the object would either be at rest, or moving at a constant Velocity.

3. Velocity: Velocity is basically speed but in a specific direction, and formulas for getting speed are,

                            v = at,    or v = d/t

Adding to these formulas we also had to differentiate between graphs that had increase decrease or constant acceleration

4. Speed: Speed is the distance an object travels at a specific time but in any direction.

5. Acceleration: Acceleration is the increase of Velocity overtime. Formulas are:

                                             d=1/2at^2,       a = change in v/t

If an object is accelerating it can never have a constant velocity vise versa. The different graphs showing increase, decrease and constant acceleration are one of the more challenging things we learnt

6. Problem solving questions: I learnt the basics to solving a problem that we either still didn't learn or exceeded our difficulty, this helped me a lot, with other algebra 2 questions as well.

 

B-

The experiments we did with the hovercraft really helped me visualize the topic and helped me remember it in the test. Every time I throw a ball in the air I remember the experiment when it stated that there is no force making the ball move upwards.

The car video, which showed that a person in the car will continue to move when the car slows down as it was already moving, this was another, thing that helped me visualize the experiment in the test.

hovercraft blog post

Hovercraft Blog Post

Riding the hovercraft felt a bit weird and cool at the same time. It is definitely a great experience but the concept of it moving without any forces acting on it is pretty nice, for the people that have not tried it yet, you are up for a surprise. Its different than riding on a sledge or skateboarding as you are hovering, so you move without any forces acting on you while not touching the ground. 

From this experiment i managed to learn that it is possible for an object to be moving without any forces being acting on it, this refers to newtons first law which states, An object in motion or at rest stays in rest or in motion unless acted on by an outside force. So the hovercraft kept moving as it was moving in the first place and there are no forces affecting it. 

Acceleration always depends on forces affecting a certain object, so if the net force of an object is not 0 then there is an acceleration going on. Which occurred at the push and stopping parts of the hovercraft experiment. 

Constant velocity is when an object is moving at a constant speed in a certain direction. Relating it to our experiment, after the person on the hovercraft was pushed, there wasn't any forces acting on the object (Net force = 0) so it moved at constant velocity (equilibrium) until it reached the stopping point the force of the person stopping it made it stop. 

Some members were harder to stop than others as they weighed more, so you had to put in the same effort to move them (push them) and to stop them, so because they weigh more the amount of force you have to put it to start and stop them is much more.

Inertia

This video states clearly Newton's law of inertia, and shows an example by using the car and the seat belt. The video states that if you do not have a seat belt on and the car crashes, the car will suddenly stop due to the crash force, but you would continue to move forward causing you to hit the windscreen. But if you have the belt on a force is acting on the car and on you, so you both stop, it also explains the use of the head rest in the same way.

Introduction to physics

Ali Saeed

Why Physics

This year in Physics, I expect to learn:

• How to workout the speed height or time in which an item is dropped from.
• How to workout the acceleration of a moving object.
• What circuits are and how they work. 
• The basic rules and laws of physics
• Know how to set up and prove most basic experiments

Why is physics important?

I think that physics is the number one source that explains to people why certain objects act the way they do, it explains every single movement, acceleration, drop, to as simple as a equation. It is the problem solver of the universe, It indicated what is possible and what is impossible. All of the current day technology and development have been possible only through physics, without physics there would be no technology no light no entertainment. 

 

What do you think problem solving is?

 

I believe that problem solving is the process of getting the solution of a certain complex problem through a series of experiments, calculations and observations. Repetition is also key to problem solving as it assures the reliability of the solution.

 

What questions do you have about physics?

 

The questions that I have constantly been getting confused about is:

• The difference between energy and power?
• An explanation of what dark matter is, or what its place in the universe is?

 

What goals do you have for yourself in physics this year?

 

In physics I plan to be interacted with whatever the class is doing at all times, and to be fully aware and understand what is going on in class, rather than just copying or effortlessly doing work. I am also a great lover of physics so I would hopefully want to get a clearer idea of what physics section I mostly feel comfortable in, which will also hopefully lead to me knowing what I want to major in University.