Unit Summary
Here is what I learned during the first Physics Unit...
→Inertia
Have you ever left something on the hood of your car, forgotten it was there, and driven off? If you have experienced this, you may wonder why the object, lets say a to go coffee cup, fell to the ground as you drove away.
This can be explained by Newton’s First Law, stating that objects in motion will stay in motion, and objects at rest will stay at rest, unless an unbalanced force is exerted upon it.
The hardest idea to grapple with while learning about inertia is why exactly objects keep doing whatever it is that they are doing. The answer is that they continue performing their actions purely because they are “lazy” in a sense, and they want to keep moving in the direction they have been moving, until something stops them. This concept cannot be further explained; it just has to be excepted.
….So why did the coffee cup fall? Both the car and cup were at rest, then when you drove away, the car was in motion, but the cup remained at rest. The cup essentially pulled out from under the car as it drove away, then gravity pulled it to the ground.
→Equilibrium and Net Force
If an object has a net force of zero Newtons, it is at equilibrium. This can occur when the object is moving at a constant velocity, or at rest. Net force is the total combined forces being exerted on an object at a given time. Watch our short video for more information on Equilibrium and Net Force!
→Speed and Velocity
Speed and velocity are easily confused. The thing that differentiates the two is that velocity requires an object to change it's direction. Speed is the amount of time that it takes for an object to cover a certain distance. In other words, if an object’s velocity is changing, then its direction is also changing. Let me give you some examples to help you better understand...
If a runner is running laps around a track, they can maintain a constant speed, and also have a changing velocity. This is because they are changing their direction as they run around the track, therefore they are changing their velocity.
On the other hand, it is impossible to have a constant velocity and a changing speed at the same time, because maintaining a constant velocity means maintaining a constant speed.
Here are the equations for constant velocity…
When you want to know how far an object has moved at a constant velocity, use d=vt
When you want to know how fast an object is moving at it’s constant velocity, use v=d/t
→Acceleration
Acceleration is a measure of the change in velocity over a given time period. In other words, it is the rate at which an object is gaining or reducing it's speed. An object can be accelerating when it is changing it’s direction, increasing speed, or decreasing speed. Acceleration is measured in m/s2
a=change in velocity/time
For example, when a you were little and liked to roll down hills, you were accelerating, because your speed was changing as you descended. The steeper the hill, the greater the acceleration. And finally, gravity causes all objects to accelerate downwards at a rate of 9.8m/s2
When you want to know how far an object has moved at constant acceleration, use d=1/2 at2
When you want to know how fast an object has moved at a constant acceleration, use v=at
→Graphing
Learning how to use graphs and data was a huge challenge for me. I will break it down into a few steps to make it easier to understand
1. After you create a graph, record the equation of the line in the form of y=mx+b
Ex. y=5x
2. Once you have your equation using excel, change it into words
d=y x t2
3. Now, look at the equation you have, and compare it to the other physics equations. Which one does it look the most like??
d=1/2 at2
4. Compare the equations from two steps above. What value is missing in the formula on question 2?
½a
5. In this case, 1/2 a is the slope of the line
½ a=slope
½ a=5
6. Use the above information, and solve
5= 1/2 a
a=10m/s2
