Week 4 Blog Post

  This week's big question was "What affects how long it takes a swing to go back and forth?"

Lab

In Lab this week, we first clarified and expanded on concepts of acceleration, normal force, friction, and what weight is. We watched the BBC video where they dropped a bowling ball and feathers in a vacuum to demonstrate that gravity causes objects to fall at the same rate, despite different weights. We clarified that gravity pulls harder on more massive objects, but more massive objects take more force to accelerate- even when falling straight down. 

Next, we began talking about our question for this week. The different variables we came up with for affecting a swing's period were chain length, weight, rider position, outside forces, wind, or age of the swingset. My group decided to test the length of the chains. We found that chain length does have an impact on how long it takes to swing back and forth. As chain length increases, the time it takes to swing back and forth increases as well. 

Lecture

In Lecture this week, we discussed what we'd learned from the lab. We talked about how the reason why weight doesn't affect a swing's period is the same reason the bowling ball and feathers fall at the same rate without air drag. Even on a swing, the heavier object is harder to accelerate but is pulled on harder, while lighter objects are easier to accelerate and are pulled on less. 

We then looked at two of Newton's laws: 

1. Without an unbalanced external force, an object will maintain its speed and direction of motion. 

2. The amount an object speeds up or slows down depends on its weight. 

Next, we talked about why the longer rope/chain meant that it took longer to swing back and forth. To summarize, the longer the chain, the farther the object has to go, but it has the same potential energy as an object on a shorter chain (if dropped from same height). Even with different lengths, the objects will swing at the same speed at the very bottom because they are maxing out their kinetic energy.  

We wrapped up with an explanation for why we need to keep pushing kids on the swings if they aren't pumping their legs. The reason is because the object collides with tiny particles as it moves through the air. These small collisions create transfers of energy from the pendulum to the particles, which then move around faster. The energy that was in the pendulum system is now in the air as thermal energy because the particles are colliding with each other. 

Pressbook

What did you learn?

I learned that the angle of release only has an effect on the period at larger angles. And in that case, the larger the angle, the longer the period. 

What was most helpful?
Something that helped me was all the "real life" examples to explain the concepts in this chapter. The wrecking ball helped me to conceptualize and apply my understanding of kinetic energy, and the grandfather clock example helped me understand how the concept of a pendulum is used in practical applications. 

What do you need more information on?

I could use some more information on how to explain the concept of a pendulum to kids, and at what age most curriculums introduce pendulums. I have a decent conceptual understanding but would like to start learning how to make the concept approachable for students. 

What questions/concerns/comments do you have?

I want to look into Focault's pendulum more. It seemed really interesting and I would like to learn more about how it works and how it demonstrated that Earth is rotating on an axis!