Newton's second law states that acceleration is directly proportional to the force of an object, but inversely proportional to the mass of an object. We used these equations:
a=f
a=1/m
For example, if a box was pushed with 2N of force compared to a box pushed with 5N of force, the box with 5N would accelerate more. If two boxes had 2N of force exerted on them, but one box weighed 10kg and the other weighed 5kg, the box weighing 5kg would accelerate mare than the box weighing 10kg.
In free fall, and object has only one force acting on it once it leaves its support force, this is the force of gravity. The force of gravity causes the object to accelerate at the constant rate of 9.8m/s^2, but in class we rounded it to 10m/s^2 unless we were working on a lab. Since the only force working on the falling object is gravity, the acceleration is equal to the forge of gravity (a=g). If you would like to find the velocity an object is falling at you use the equation v=gt In order to find the distance an object has fallen in free fall you use the equation d=(1/2)gt^2. You can rearrange these equations to find the time or solve for another variable depending on what information you have.
When falling through the air, an object has the force of air resistance against it. When the force of air resistance is equal to the weight of the object falling (their net forces are equal) the object is at equilibrium or terminal velocity. For example, what would fall to the ground first, a ping pong ball or a lead ball? Who would ave a greater terminal velocity?
If you dropped a ping pong ball and a lead ball at the same time from a tall building, the lead ball would fall to the ground first because it has a greater weight and needs more air resistance to reach terminal velocity. Since it needs more air resistance to reach terminal velocity, it has a greater terminal velocity than the ping pong ball.
If you had dropped the balls from a moving air plane, then you would have to factor in the horizontal velocity. The balls would go the same distance vertically but would continue to move horizontally at the initial rate of the plane when they were dropped. So if the plane were going at a constant velocity then the balls would reach the ground directly under the airplane even though it was moving.
Another aspect to falling through the air is the surface area. An example of this is a parachute, if someone falls through the air and reaches terminal velocity, in order to land safely the open up a parachute. The large surface area catches the air making the force of air greater than the parachuters downward force. In order for the parachuter to reach terminal velocity and have equal net forces again, the velocity of the parachuter must decrease. So a greater surface area, the lower the velocity.
Projectile motion was one of the more difficult things we learned in Unit 2. There are many different variables that effect projectiles including gravitational force, horizontal velocity, and vertical velocity. It is important to know that the horizontal velocity is constant throughout the projectiles motion like when it is free falling. Once a ball is projected through the air it reaches a peak of 0m/s vertically but would still be moving forward however fast it was horizontally. Then it begins to descend where its vertical velocity increases until it reaches the ground.
I could use the things I learned in this unit to determine how far I should go in order to throw a ball at a target or if I ever wanted to go skydiving, I would have a better understanding of when I was going at a constant speed and when I should start my parachute. I could have done better on my podcast, i wish i had been more detailed on Newtons Second Law. I think i dod very well on doing my homework and asked good questions in class. I really like the video homework we are given, it gets me an idea of what i should ask my teacher the next day in class.
This is my Podcast on Newtons Second Law :
