Term

Definition
Walk towards the origin slowly, gradually increasing your speed. 


Term

Definition
Walk away from the origin slowly, gradually increasing your speed. 


Term

Definition
Walk away from the origin slowly, gradually increasing your speed.



Term

Definition
Walk towards the origin quickly, gradually decreasing your speed. 


Term

Definition
Walk away from the origin quickly, gradually slowing down. 


Term

Definition
Constant Speed Away from the start 


Term

Definition
Measured in meters
From the start to the finish (not distance which is the entire path) 


Term

Definition
In relation to a reference point
If a bus is moving 20 mph and you walk 1 mph to the front, then you ADD the velocities. If you are walking from the front to the back, you subtract 


Term

Definition
Law of Inertia and car crashes
The more mass you have, the more inertia you have.
Inertia determines the ability to make something stop or change its motion. So, it is easier to change the motion of a baby stoller than it is a school bus.
More mass = more inertia 


Term

Definition
F = m x a
measured in Newtons
If something is falling or the mass is affected by gravity, you can use
W (weight) = m x g
Why? Weight IS a force due to gravity. 


Term

Definition
Action and Reaction Pairs
Equal Forces in opposite directions
You hit the wall and it hurts because the wall was hitting you!
If the bug hits a windshield, we are sad that the big died, but the bug put the same force on the windshield that the windshield put on the bug 


Term

Definition
Object is NOT at rest...look at y axis!
The object is moving at a constant velocity 


Term
What should I study for the semester exam? 

Definition
1. All your old chapter tests that we taped into your notebook
2. The notes on graphing
3. CBA 1 and 2
4. The practice semester exam we did in class yesterday
A lot of the questions are similar or even the same, so please review the old tests and CBAs!!!!!!!! 


Term
1. Which object has a greater inertia?
A. 2kg object moving at 6m/s
B. 3kg object moving at 5m/s
C. 6kg object moving at 0m/s
D. 7kg object moving at 1m/s 

Definition
D. An object with more mass has more inertia 


Term
Law of conservation of energy 

Definition
Potential has to do with how high something is
(GPE = m g h) and Kinetic has to do with how fast something is going (KE = 1/2 m v ^2)
Potential is converted to kinetic as an object falls
The potential at the top is 100% and the kinetic is 0%. By the time the object hits the ground, it is moving the fastest, so its kinetic is now 100% and potential is 0%. 


Term

Definition
work is measured in JOULES
Work = change in kinetic energy
work = force x distance
example: If you walk up the stairs, like in our lab, you walked up a distance of 2.16 meters. We would multiply your force by the distance you went UP from the ground.
What happens if you don't have the force???
Well, you have to do (m x g) to get the force! 


Term
Work = change in kinetic energy 

Definition
The amount of work you do is equal to the change in kinetic energy.
Let's say you drop a 2 kg ball from rest and by the time it hits the floor it was going 10 m/s.
Work = the change in KE
So you have to calculate the KE initially and then the KE from when it hits the ground and then subtract. 


Term
Law of conservation of momentum 

Definition
momentum before = momentum after
the velocity may change when something is hit that was originally at rest, but their momentum will never change 


Term
With projectile motion, when do I use
v = d/t 

Definition
...when you are solving for a horizontal throw! 


Term
With projectile motion, when do I use:
d = vit + 1/2 at^{2}
converted to:
y = 1/2 gt^{2}


Definition
We use these formulas when we want to know how far down something has fallen or how high the cliff is. 


Term
When do I use "g" instead of "a"? 

Definition
If something is falling or being dropped, gravity is a factor, so you would use g = 9.8 instead of solving for "a".
For example, if you are lifting a 20kg dog 3 meters and want to know the work:
w = f x d
w = m x g x h
w = 20 kg x 9.8 x 3 m 


Term
A 5kg box is being pushed with a force of 20 N up a 10m ramp that is 4m off of the ground. How much work would be done to lift the box to the top? 

Definition
Since work = force x distance,
W = 20 N x 4 m = 80 J
You don't use the mass because we already know the force (and don't need to do f = m x g to get it) and we want to know how high the box was lifted, not how long it was pushed, so we don't use the 10 m. 


Term
A resultant vector represents the sum of two or more vectors. If Juan walks 200 m east and then 600 m west, What is his displacement (including direction)? 

Definition
400 m west
Why?
He is walking in two different directions, so you subtract. 


Term
Alex throws a football off the top of the school to a friend below. He throws the ball at 2 m/s. The school is 10 m high. How much time does it take for the ball to hit the ground?


Definition
Remember, time to launch (horizontally) equals time to drop (vertically).
So, you can use y = 1/2 g t^{2}
10 = 1/2 (9.8) t^{2}
t^{2}=2.04
square root both sides
t = 1.43 s



Term
What is the impulse of a 10 N force acting westward on a car for 5 seconds? 

Definition
Impulse = force x time
10 n x 5 seconds = 50 N s westward 


Term
When friction is applied to an object in motion, what does the kinetic energy convert to as it slows down? 

Definition
Friction can cause energy to be converted to heat. 

