Torque

This weekend while I was driving, I recalled what we had learned about torque in class and how the steering wheel of a car has torque. Torque is a force that causes or opposes rotation. It causes angular acceleration and makes an object want to change its state of rotation. While turning, there is an axis of rotation and a force being applied by my hand. The radius of the wheel is the lever arm. By using torque, I am able to steer and turn the car in the direction I apply the force in. I never realized that torque is responsible for how I steer while driving. Physics is everywhere!

Impulse

I never stopped to realize that karate has something to do with physics. Every time I throw out a punch, I am exerting an impulse that is equal to the amount of force I put in to the punch multiplied by the amount of time I exert that force for. Impulse is equal to the change in momentum. Punching someone is almost like a sticky collision and momentum is conserved no matter what, so the initial momentum should equal the final momentum. Also with this in mind, almost all of my punches exert the same impulse, but the stronger punches are the ones with more force done in less time, rather than the ones done with less force in more time, so quick jabs are much more effective in sparring. I always knew that fast punches seemed much stronger than the ones I took my time on, but I never knew the reasoning behind this until we recently started learning about momentum and impulse.

Potential and Kinetic Energy

In class, we are learning about potential and kinetic energy. At the top of the slide before I started sliding down, my potential energy in relation to the bottom of the slide is equal to my mass times 9.8g times the height from the top of the slide to the ground. My kinetic engery at this moment is zero because kinetic energy is equal to half of my mass times velocity squared, and I have zero velocity. As I started sliding down the slide, my kinetic energy raised because I was gaining velocity, but my potential energy lowered because the height was lowering. Althought the potential and kinetic energy was changing as I slided down, the total energy (potential + kinetic) remained constant at any point. This explains the conservation of energy. At the bottom of the slide, I came to a stop and my potential and kinetic energy both became zero.

First Quarter Reflection

Physics is a very challenging course. I never expected it to be this difficult. I usually am a person who enjoys math more than memorization. I liked Chemistry last year much more than Biology because it involved more math problems. I thought Physics would be the same, but it makes me think very hard just to solve one problem. All of the different forces and their directions are quite confusing. Although tests and quizzes are difficult, I enjoy the labs in this course. They are very fun. I also enjoy the class environment. I like how it is laid back, and we get the chance to work with everyone. I'm pleased with my performance in this class so far, but I still hope to do much better by studying and practicing more problems. My goal for this course is to be able to do every concept with ease. I'm scared but very excited for what's to come this school year in Physics and expect to have fun, and all of this is shown in the picture above from Halloween a year ago.

Newton's 1st law

In 8th grade, we were taught about Newton's Laws and learned that his first law stated that an object in motion stays in motion and an object at rest stays at rest until a net force acts upon it. I wasn't really sure what this all meant in 8th grade, but learning about his laws more in depth in physics helps me to understand his laws a bit more. According to Newton's 1st Law (law of inertia), every object continues in its state of motion until acted upon by a net force. The object's state of motion is either at rest or at a constant velocity. At this state, the object's net force is zero. While at a sleepover, we piled the drink bottles up on each other, and they were all at rest. Because of Newton's 1st Law, the bottles stayed at this state of motion until a net force (someone's hand) broke this state and pushed the bottles over. This incident happened a while ago and was something we did only for fun because we were bored, but it is interesting to know now that there is physics related to this.

Projectile Motion

While playing tennis, there is actually physics related to the sport. Projectile motion is "the movement determined by an object's initial velocity and the constant acceleration of gravity." This works when there is zero air resistance. When I hit the ball, it starts traveling across the court at a certain velocity until it gradually changes due to gravity. The ball bounces on the ground, and then the other player hits the ball back. The horizontal velocity put on the ball never changes throughout the ball's flight. The time it takes the ball to bounce isn't affected by the amount of horizontal velocity the ball has, it is depended on the initial velocity and gravity put on the ball. This projectile motion may be more obvious when a lob is hit because the force of gravity acting upon the ball's initial velocity can easily be seen. The ball is hit up and falls back down because of its acceleration of -9.8 m/s/s, but the ball never changes its horizontal velocity until it hits the ground because there isn't a force changing it.

Velocity and Acceleration

This past summer I went to Las Vegas with my mom, sister, and Blake. While we were there, I rode the roller coaster at Circus Circus with my sister. This ride showed the physics of velocity and acceleration. Velocity describes the speed and direction of an object, while acceleration is any change in velocity over a period of time. The roller coaster's velocity was zero at the start of the ride. As we started moving up the track, it started to accelerate from rest to a slow speed and then maintained that speed for a constant velocity until we got to the top of the slope. After reaching the top, we accelerated again until we reached the peak velocity and couldn't accelerate anymore. We maintained this velocity throughout the ride until we started to slow down and experienced negative acceleration towards the end. The ride finally came to a stop for zero velocity again. We moved in the forward direction for the entire ride. We ended at the same starting position as the beginning, so there was no displacement during this ride.