Physics Blog #9 Light Switch

This video demonstrates a light switch. By increasing/decreasing the resistance, the light affects the current, or the amount of charge over time. Ohm's law, I=V/R demonstrates this because if R is higher, than I is lower.

 Less current means less power, as shown by the equation P=IV. So because V is a constant 120V (from the outlet),  current is the only thing that affects the power. By increasing current, I can increase the power and brightness of the light, or by decreasing the current, I make the bright dimmer.

Physics Blog #8 Bigger is not always better

I was running out of ideas to do my physics blog when I saw this amazing scene outside. Theoretically, if buildings did not have lightning rods, it would be better to be a small building, as show in the picture. 

The bigger and taller buildings (that I pointed out) would be more prone to lightning strikes because they are closer to the polarized, negatively charged underside of clouds that want to be neutral (which explains why in the times before lightning rods, tall buildings were more frequently hit). So it would be better to be a small building because you are shielded by the bigger ones.

Luckily, somebody invented lightning rods, which prevent big buildings from being shocked. When lightning strikes, it hits the lightning rod and is harmlessly conducted into the ground by a wire.

I also found this funny cartoon that made me laugh a lot because i love physics.

(Late) Blog Torque!

This is a pool cleaner that we use at my house. I realized that the equation for torque, t=fr, applied to it.

In order to increase the amount of torque exerted I could lengthen my lever arm. For instance, the farther away my grip from the net, the more torque I have.

I could also increase my torque by increasing the force at which I swing the pool cleaner with.

Finally, I could also make the angle of my lever arm more perpendicular to the wrench, which would result in a larger r and therefore a larger F.

The moment of inertia concept also applies to the cleaner. If I grasp the cleaner closer to the netting, my moment of inertia would be smaller because my r or l is smaller. This also means that it would be harder to start or stop the pool cleaner.

(Late) Blog Static Equilibrium Light

This light demonstrates static equilibrium.  The combined tension in the two rods must be equal to the downward force of the lights and the wooden support. The resulting equation would look like:

T1sintheta+T2sintheta=mglight1+mglight2+mgwood

We can also know that because the light is at equilibrium, the net torque is 0. To find the net torque, we can use the equation Tccw (counter clockwise) -Tcw (clockwise)=T=0.

To solve the problem, you could use either end as the fulcrum. For instance, if the left side (when looking at the picture) was used as the fulcrum, than the equation would be:

T2y(r)=mglight1(r)+mglight2(r)+mgwood(r)

After finding T2y you could then find T1y.

Physics Swing Circular Motion Blog #5

This swing shown in this video displays several properties of physics.  If I had the variables, I could find it's linear acceleration, which is a change in speed.  The linear acceleration can be found by using the equation a=∆V/t.  Since the swing was also moving in a circular motion, it has centripetal acceleration too! In caveman terms, centripetal acceleration is a change in direction, which the swing is certainly doing. The equation for centripetal acceleration is ac=mv^2/r, or alternatively, ac=ω^2r. We can also find ω (wumbo) from the equation. Wumbo is the symbol for angular speed, which can be measured in rpm or rad/s. In other languages, wumbo also is a verb and a noun.

If I have wumbo, then I can also find my linear velocity using the equation v=rω. The swing has linear velocity, linear acceleration, angular speed, and angular velocity. Next time I go on it, I will try to increase my velocity by increasing my rpm (ω) as well as my radius.

Physics, Anger, Energy Blog #4

Today, I was really angry that I bombed my physics test. In order to release my anger I threw a real cow at a surfboard. I felt sorry for the surfboard afterwards. The cow was okay though.

The formula for work is W=F*displacementX(costheta).  Where W is work and F is the force.  So by finding the distance traveled by the cow and the force my cannon arm applied to the cow, I could find the work done.

By finding the work done, I can also find the velocity of the cow. Unfortunately my cow was a baby and weighed too little to be registered on the scale, but by using the formula: W=KEf+0 (because there is no initial KE), because KE is 1/2*m*v^2, I could find the velocity. Alternatively, I could find the weight if I had the velocity. However, I think that even though this cow seemed to weigh a ton, the velocity would be too high for me to calculate due to the enormous amount of work done.

I could also calculate my power by dividing my work done by the time it took for the cow to hit the surfboard (.000009s?). P=J/t. Then I could find my horsepower by dividing the power (in watts) by 746...but that would be too much WORK for me to do...

Swing: Newton's Third Law

 

Newton's third law states that for every action, there is an equal and opposite reaction.  Meaning that if A pushes B with x amount of force, than B pushes back with x amount of force, or, if A pulls B with x amount of force, than B pulls A with x amount of force.

In this video I demonstrate Newton's third law.  I push the swing with x amount of force, causing it to go forward (the direction I push), the swing pushes back at me with an equal amount of force.  However, the swing moves more because it accelerates more.  Using Newton's Second Law's equation (a=net force/mass), it makes more sense.  Since the swing has a lot less mass than me, it accelerates more.  But, because I comparatively have a lot more mass, my acceleration (backwards) is very small.