Q&A on Circular Motion

This is a Slow Motion video of how the water in the bucket is not spilling out because of centripetal force

Q: What is centripetal force?

A: Centripetal force is what we call a force that is perpendicular to motion. A centripetal force can be any force, gravity, tension, friction, but it must be perpendicular to the motion of the object.

Q: Why is centripetal force circular?

A: Centripetal force is circular because the force acting on the object is a continuous perpendicular force. If the force is not constantly being acted upon the object, then it the motion will not be circular.

Q: What are some examples of centripetal force?

A: A car uses centripetal force to turn: the friction of the tire on the ground causes the turn. Also, a swinging a ball on a string uses centripetal force because the string has a tension force, causing the ball to move in a circle.

Q: If you were to cut the string attached to the ball as it was moving, what would happen?

A: The ball would move in a straight line in the direction of the velocity because of inertia. Here's a picture that better explains it: 

Q: What is centripetal acceleration? 

A: For every unbalanced force, there is acceleration. Because centripetal force is not a balanced force, there is centripetal acceleration. Centripetal acceleration is in the same direction as the centripetal force, which is ALWAYS inward. To calculate centripetal acceleration, use this equation: 

Ta-da! Hope you now have a better understanding on centripetal force!

The Catapult Project

Wow! What a relief. For the past few weeks, I have been working with my fellow lab table mates on a catapult. This was quite the project. We had to consider many different forces and laws to make sure our catapult would, first of all, actually work when made of popsicle sticks, and secondly, launch farther than one meter. We were able to launch our catapult more than one meter, but the process to get there was very difficult.

When first starting, we drew out our catapult. I used a design I found from stormthecastle.com, a site which I found some very creative designs. I chose a triangle shaped catapult for it looked the simplest and easiest to change if something went wrong. After beginning, our group decided to build a platform for our catapult and also make the arm longer so the golf ball we were launching would go farther. Next, we agreed on making our angle of launch at about 47˚ because, when we were practice launching, that gave us the best distance. We also knew gravity, which would affect the golf ball's inertia, would be a pretty big factor, so we used a lot of tension force (all rubber bands) to get our arm to launch fast, which also increased the acceleration of the golf ball, therefore causing it to launch farther. Although we could not control the mass of the golf ball we used, we made sure that the force on the golf ball was great so, again, the golf ball would be able to accelerate. Finally, we made sure to hold our catapult down when shooting so it would not come back and crack the popsicle sticks holding the arm straight.

My whole group really enjoyed this project, and if anyone ever has some free time, I would definitely try making a catapult. It is fun and really helps you realize how forces affect real life!

Our Catapult!

What is a Scale and What is it Measuring?

I found this video quite funny. 

So does a scale measure weight? No! A scale is used to measure the amount of force you are pushing on the scale due to the amount of force you are pulling on Earth. Although your mass should be in Newtons, it is is pounds because you divide your weight in Newton's by 9.8 m/s2 because of acceleration. 

Here's a cool article that explains the difference between weight and mass:

http://www.mathsisfun.com/measure/weight-mass.html

Are they Really the Same?

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Newton's Second Law and Newton's Law of Gravitation use two very specific equations to calculate force. The Second Law states that Foce is equal to Mass times Acceleration. The Law of Gravitation states that Gravitational Force (Fg) is equal to G (the gravitational constant) times the Mass of the first object times the Mass of the second object divided by the Distance squared between the two items. Both equations solve for force, but are they the same?

The two laws can be the same! If when solving for Newton's Second Law you are solving for the gravitational force on the object, then the two equations equal one another. However, if you are using F=ma to solve for a different kind of force, like magnetic or friction, you can not you the gravitational force equation.

The mystery had been solved!