Unit 2 Reflection

Topics Covered This Unit

Free Falling (straight down)         Free Falling (throwing things up at an angle)

Free Falling (at an angle)                    Free Falling (throwing things straight up)

 Newton’s Second Law                        Falling with Air Resistance (Skydiving)

Important Relationships

“Acceleration is directly related to force and is inversely proportional to mass.”

a=F/m

Important Equations

d=(1/2)gt²        a²+b²=c²

v=gt                     v=d/t

What Equations go with What

	Vertical	Horizontal
How Far	d=(1/2)gt2	v=d/t
How Fast	v=gt	v=d/t

Newton’s First Law

a=F/m              w=mg              a=1/m              a~F

“Acceleration is directly related to force and is inversely proportional to mass.”

To increase acceleration, increase the force, or decrease the mass. To decrease the acceleration, decrease the force, or increase the mass

Translating it to graph:

y=mx+b à acceleration=Fnet (1/m)            slope= fnet

Falling with Ari Resistance (Skydiving)

	Increasers of Air Resistance
1.)	Increase of Surface Area
2.)	Increase of Speed

When a person falls through the air, their acceleration decreases, their velocity increases and their Fnet decreases

acceleration=(Fweight-Fair)/(mass)

When a person opens their parachute, their acceleration changes direction (because Fair is larger than Fweight), their velocity stays same direction but slows down (because person is still falling), and their Fnet changes direction (upwards) because Fair is larger than Fweight.

Why does a lead ball hit the ground before a ping pong ball when dropped from a building and not when falling from a table?

This is because from the building, there would be enough time for the two balls to reach terminal velocity. The steel ball will go faster because it has a greater weight than the ping pong ball. This makes the lead ball have to compensate by going faster, which increases it’s Fair.

How do the velocities,  acceleration, and net-forces compare when a skydiver is skydiving without the parachute open, and after the parachute is open (both times in terminal velocity)?

The only thing that is different between the two is that the velocity is slower. Netforce is the same, and acceleration is the same because the weight of the diver does not change, meaning their F-weight does not change, meaning that if the diver is to reach Terminal Velocity, it must retain the same F-air, meaning the net-force is the same.

During Terminal Velocity…

Acceleration is 0m/s²                                   Velocity is constant

Netforce is 0N        Diver is at their fastest point possible

Free Falling (Straight Down)

THE ONLY FORCE IS GRAVITY

Weight does not matter

“When an object falls due to the effect of gravity ONLY”

How Far	d=(1/2)gt2
How Fast	v=gt

acceleration=gravity

Free Falling (at an angle)

The only thing that determines time in the air is vertical height

	Vertical	Horizontal
How Far	d=(1/2)gt2	v=d/t
How Fast	v=gt	v=d/t

Falls in a parabolic curve

Free Falling (throwing things up at an angle)

a²+b²=c² will help you find actual velocity

These are special triangles that will appear on a test. The Hypotenuse is the actual velocity (c)

	Vertical	Horizontal
How Far	d=(1/2)gt2	v=d/t
How Fast	v=gt	v=d/t

Acceleration at the top of an object’s path will be 10m/s² because of gravity

Velocity at the top of an object’s path will be the horizontal velocity because vertical velocity=0

Free Falling (throwing things straight up)

Always measure things from rest, meaning measure time and distance from the top of an object’s path, down.

Velocity at the top of an object’s path will be 0m/s

Acceleration at the top of an object’s path will be 10m/s² because gravity does not stop working.