1. Newton's Second Law
2. Air Resistance
3. Free Fall
> Straight Down
> Thrown Straight Up
>Thrown Upward at an Angle
> Projectile
>> Newton's Second Law
Newton's Second Law states that acceleration is directly proportional to force, and inversely proportional to mass. This can be defined in the following equation:
a = F/m
Another way this equation is shown is
F=ma
One thing that is key in Newton's Second Law is remembering that weight and mass are two different things, thus they are not interchangeable in an equation.
For example, if the given mass of an object is 10kg, you must find the weight. You do this by using the following equation:
W=mg
Which means weight equals mass times the force of gravity, which is always 10m/s^2. So, if the given mass is 10kg, times the 10m/s^2 force of gravity, the weight of the given object is 100N (since weight is always written in Newtons).
>> Free Fall: Straight Down
Free fall is when an object is falling down with only the force of gravity acting upon it.
There is no air resistance in free fall. So, the only time free fall can happen is when it is in a vacuum.
There is no air resistance in free fall. So, the only time free fall can happen is when it is in a vacuum.
In free fall, the object with accelerate at a rate of 10m/s^2.
In order to calculate the distance that the object has fallen you use the formula:
d= 1/2(g)(t)^2
Which means, distance equals one half gravity times time squared.
When calculating how fast the ball was going when it hits the ground, you will use the formula:
v= gt
>> Free Fall:Straight Up
The difference between normal free fall and being thrown straight up is that when something is thrown up, it has an initial velocity.
Due to gravity, the object will decelerate at a rate of 10m/s^2 on its trip up, and will gain speed at the rate of gravity on its way down.
We are still able to use the equation for distance that I wrote for free fall. However, you do not use the total time that the ball is in the air, you use the time it took the ball to reach the top of its path.
>>Free Fall: Projectile
Projectile motion falls at the same rate as something in free fall would, however, there is also a horizontal velocity. So, when dealing with projectile motion, one must take both velocities into account.
Horizontal velocity will remain the same as the object travels. In order to find the horizontal distance you will use the equation:
In order to find the time the object is in the air you will use the equation:
d= 1/2(g)(t)^2
which you can then plug into the horizontal distance equation.
Remember that when you are trying to find exact velocity, that you can make right triangles out of horizontal and vertical velocities. When both legs of the right triangle are equal, the hypotenuse is equal to that number time the square root of 2, which equals 1.41.
>>Free Fall: Thrown Up at an Angle
This combines the skills that we learned in throwing straight up, and projectiles. You will use the same equation as before to find the distance from the ground at the highest point:
d= 1/2(g)(t)^2
And you will use the same formula to find the horizontal distance the object will travel:
d=vt
Also keep in mind what I said about exact velocities.
>> Air Resistance
There are two things that change air resistance:
>Speed
>Surface area
As the speed or surface area increases, the air resistance will increase, as well.
If a person were to jump off a building, their Fweight will be greater than their Fair (air resistance). In order to reach equilibrium, or terminal velocity, the person increase their speed to reach a point where air resistance will balance it out.
Here is my group's video for this unit.
