Unit 2

A. Newton's Second Law

• Can be defined as a=f/m
• This is the same as a=f*/(1/m) 
• Describes the relationship between acceleration and mass and the relationship between acceleration and force
• Force is directly proportional to acceleration
• This means that as force goes up acceleration goes up
• Mass is indirectly proportional to acceleration
• This means that as mass goes up acceleration goes down

B. Newton's Second Law Lab

• In the first lab we manipulated the mass of the system by adding mass to the cart an leaving the force/mass of the hanger the same
• As mass increased, the acceleration went down
• When we graphed the line of the data we gathered, we found the slope to be .468 
• The force from the hanger was .5N 
• The reason why they are so close is because the force was the constant so it will also be the slope of the line
• In the second experiment we manipulated the force
• In order to ONLY manipulate the FORCE we had to keep the MASS of the system CONSTANT
• This means that we had to start with a lot of mass on the cart and over time add it to the hanging weight
• If we just added weight to the hanger then we would be manipulating two things affecting our data
• We found that as the force went up the acceleration of the cart went up
• We found that our slope was .102 and the mass/constant was .1058 which were very close
• Both experiments thus proved Newton's Second Law

C. Falling through the Air

As you fall your velocity increases and so does your air resistance

• When you're falling through the air, gravity is no longer the only force acting upon you
• Air resistance begins to impact you as your velocity increases
• Since your velocity begins at 0m/s your air resistance begins at 0
• When you first jump you have a velocity and net force of 0
• Due to gravity (10m/s^2) you begin to fall
• As you fall your velocity goes up
• As velocity goes up, so does your air resistance 
• Due to air resistance, you reach a terminal velocity 
• This occurs when gravity and air resistance reach an equilibrium and your speed no longer increases
• At terminal velocity net force and acceleration are both 0
• At this speed you cannot get any faster
• Then when you open your parachute, your surface area was greatly increased causing your velocity to go down
• You eventually reach a second terminal velocity and it is much slower in 

D. Freefall

• When falling in free fall, air resistance does not affect you
• The only constant force is gravity which has an acceleration of 10m/s^2
• v=at
• If something falls for 8 seconds, we know that right before it hit the ground it had a velocity of 80m/s because 8*10=80
• In freefall,all objects fall at the same rate so an elephant will hit the ground at the same time as a piece of paper

E. Throwing Things straight up

• When you throw things up their initial velocity determines how long they will stay in the air
• The amount of time that it takes for them to go up is equal to the amount of time that it will take for the object to fall
• If it goes up for 4 seconds it will take 4 seconds to fall down
• Use d=(1/2)at^2 to solve how high it goes
• If thrown up then acceleration is negative because it is in the opposite direction
• If an object goes up at a velocity of 40m/s
• After 1s it will be moving at 30m/s
• After 2s it will be moving at 20m/s
• After 3s it will be moving at 10m/s
• After 4s it will be moving at 0m/s 
• The acceleration is STILL 10M/S^2
• After 5s it will be moving at 10m/s
• After 6s it will be moving at 20m/s
• After 7s it will be moving at 30m/s
• After 8s it will be moving at 40m/s then hit the ground
• Acceleration will not change throughout the fall
• 
  

F.Falling at an angle 

• The only thing that determines how long it will be in the air is the vertical height
• The horizontal velocity does not affect how long it will be in the air
• The horizontal velocity will stay constant throughout the fall
• Use triangles to calculate the actual velocity
• 

• Acceleration due to gravity is still 10m/s^2

G.Throwing things up at an angle

• This is the same as falling in many ways.
• Your initial vertical velocity is the only thing that determines how long you are in the air
• Your horizontal velocity remains the same throughout the rise and fall
• At the top of your path, your velocity is equal to your horizontal velocity