Monday August 30th 2010

Intro:

Today, professor Mason started class with a little bit of math review. He split people into groups and the way he did this was using 10! in reverse!

The numbers were: 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800

This put us in our TEAMS for the soap box derby lab.

Practice:

Next was a set of problems, and like usual, we did the white board thing.

1. The first problem included 2 tracks, similar in horizontal distance, but one had a groove in it.

We had to figure out which of the following was true:

a) Ball #1 would finish first

b) Ball #2 would finish first

c) Both would finish at the same time.

The answer was b) . This was because while it does speed up going down the dip and slow down coming out of the dip, there was a certain length x, that the ball traveled while moving at the faster speed that the entrance dip gave it. Therefore even if it slowed down to the same speed as ball #1, it still covered some distance at a faster speed, making it inevitably faster towards the end.

2. The second practice problem was more consistent with the experiment we would be doing in lab. This one had a cart on an incline of degree theta (-), and a Force of friction acting on it.

<<--Incline

Masses--->>

We were to figure out if indeed mass had an effect on the acceleration of the cart. To use this we summed the forces in the x and y directions and solved for a in terms of [ theta (-), mass (m), and mew ( µ ) ]

What we got was that the acceleration was NOT dependent on the mass of the cart; it cancelled out in the equation.

Lab:

We then wen into our building of the carts and testing, by various means, which car would be faster going down the ramp.

You could have used the motion detector or the video camera to derive your acceleration and test your cart with different weights to figure out how many ( if any ) amount of extra masses would help your cart achieve the fastest speed.

The winner had a speed of under one second!

1st place: BOB

2nd place: J.A.B. (My Team =] )

Conclusion:

It turns out the mass on the cart DID have something to do with the speed it

achieved and based on observations, the heavier carts were slower, the lighter

carts were faster, but there was some sort of balance that allowed the cars to travel

at optimum speeds.

Homework:

• Professor Mason assigned 4 Homework problems on Mastering Physics. (due Wednesday)
• Our lab write-ups for this Soap Box Derby are due on September 3rd. (Friday)
• We are to be reading chapter 2. (This week)
• Start the Pre-Lab for the next lab: Motion on a Level Surface with an Elastic Cord. (Optional)

My name is Jose and if anything needs clarifying, let me know and i'll do my best.