Homework - 10/18/10

A box with a mass of 3 kg is resting on an incline as shown above. The box is released from rest. (a) Determine the acceleration of the box down the ramp. (b) Determine how much time it will take the box to reach the bottom of the ramp if the ramp is 2 meters long. (c) Determine the speed of the box at the bottom of the ramp.

Homework - 10/15/10

Before his foray into teaching, Mr. Aul owned a very famous sign hanging company. He held many contracts with companies such as ENRON, Bear Stearns, Lehman Brothers, and Halliburton. The history of his career is cloudy. Mr. Aul personally hung the sign infront of his headquarters. The picture is seen above. Each cable can only support 100 N of tension and the sign has a mass of 15 kg. Find the tension in each of the cables and determine how good of a job Mr. Aul did. If the cables break, in what order do they break?

Homework - 10/13/10

Three masses are connected and hanging from the ceiling.

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(a) Determine the tension in each rope.

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The top string is then untied from the ceiling and is pulled upward with a constant force of 600 N.

(b) Determine the acceleration of each block.

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(c) The tension in each rope.

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(d) Compare the tensions from part c to the tensions from part a. Did the tension in each rope change? Was this what you would expect? Explain.

Homework - 10/4/10

A cannon is aimed at a building with an angle of 35 degrees as shown above (it's ok to feel jealous of my Paint skills). The cannon is placed 516 meters from the base of the building. If the cannon ball is fired with an initial speed of 100 m/s, determine the following quantities:

a. How high up on the building will the cannon ball land?

b. What is the cannon ball's velocity just before it strikes the building?

Assume that air resistance is negligible and ignore the initial height of the cannon.

Homework - 9/28/10

A baseball is launched horizontally from a hillside as shown above. The baseball is thrown with an initial speed of 12 m/s and lands 41.6 meters down the hill, L.
a. Determine how long the ball is in flight between points P1 and P2.
b. Determine the speed of the ball just before it strikes point P2.

Homework - 9/20/10

A bear is at a local park, drowning his sorrows the way he knows best - by drinking a mug of honey. Sad that his bear family has deserted him and that his bloodlust for humans has made him a fugitive, he slides the mug down the table in frustration. The mug slides off the table horizontally and strikes the ground 1.40 meters from the base of the table. If the tabletop is 0.86 meters high, what velocity did the mug have when it left the table? What is the mug's speed and direction just before it hits the ground.

Homework - 9/15/10

The position function below represents a rock thrown off a cliff.

a. What is the rock's displacement after the first 10 seconds of its flight?
b. What is the rock's velocity as a function of time?
c. What is the rock's velocity after the first 10 seconds? (Write the vector form, then find the magnitude and direction.)
d. What is the rock's acceleration as a function of time?
e. What is the rock's acceleration after the first 10 seconds?
f. Does your answer to part e make sense? Explain.

Free Response Review - Chapter 1

The motion graph represents a car on a straight-line track.
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(a) Describe what happened to the car at t = 1s.
(b) When is the car accelerating the most? Explain how you know.
(c) What is the car's acceleration during that interval?
(d) How far did the car travel between t = 5s to t = 7s?
(e) Plot the car's acceleration versus time.

Memorizing Equations

A touchy subject. Here's the thing, it's really easy to make an argument for not memorizing equations - that's why we didn't memorize them last year, but there's a lot more at stake now and, to put things in perspective, we're in a college course now.
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The best argument for why we should memorize equations is because you won't be given an equation sheet for the multiple choice section. And you don't want to be forced to skip multiple choice questions because you don't have an equation memorized. There aren't a ton of M.C. questions that involve using an equation, but there's enough of them to put you at a severe disadvantage if you don't know the equations. I understand it's a lot to ask, especially considering the amount of equations we deal with and memorizing them definitely takes a lot of time. I can offer a few tips to help with the process:
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1. Practice solving homework problems without looking up the equation and then checking later to make sure you've picked the right one.
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2. Keep a copy of the equation sheet somewhere visible, where you'll see it often. (I keep mine on all of the mirrors in my car. The sheer panic that's induced when switching lanes has burned those equations into my mind forever.)
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3. Try a mnemonic device or a unique way to remember the equation. (For example, I memorized the quadratic formula to the tune of pop-goes-the-weasel.)
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4. Practice them using flash cards.

Chapter 1 Review

Remember: If you can't see the image, click on it to view in another window.

1. For each of the motion graphs shown above, describe, in detail, what the motion would look like.

2. For each x-t graph shown above, create the corresponding velocity and acceleration versus time graphs.

3. For each v-t graph shown above, create the corresponding x-t graph.

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4. At a local football game (let's just say Carrick), a running back flattens a linebacker and continues running at a constant velocity of 10.5 m/s. The instant the linebacker hits the ground, he gets back up and starts running from rest to tackle the running back. If the linebacker accelerates at 1.9 m/s^2, how much time will it take to catch the runner? How far will they have traveled from their original position?

Homework - 9/2/10

A wealthy businessman has been reduced to taking the bus to work. The bus driver, assuming that a businessman certainly wouldn't be waiting for a bus, passes up the bus stop, continuing with a constant velocity of 20 m/s. The businessman starts running from rest, but can only accelerate at 1.5 m/s2. How much time will it take the man to catch the bus? Also, how far did he have to run?


At the end of this problem, explain whether this is a reasonable answer or not and explain how you know. You could also explain if it would even be possible for a human to cover that distance in that time.

Homework - 8/31/10

The diagram shown above represents two airtrack carts that are about to collide. Cart A is moving and cart B is at rest. After the collision, Cart B's position was marked every 0.1 seconds and is also shown above.


a. Based on the data given for Cart B's position create an accurate position-time graph.

b. Create a general velocity-time graph that represents Cart B's motion. You may reference the x-t graph to help create the velocity graph. (No scale needed)

c. Shade the area under the curve for the v-t graph, state what it represents, and explain what value it should have.

(READ: You need to click on the image to see a larger version)

Is AP Physics Difficult?

Not when you've got a fantastic teacher! Ha, I kid. No, seriously though, I've been asked that a lot. The answer to that question is yes - plain and simple. Now, that's an obvious answer because the AP program provides a college-level experience in high school; earlier than you'd otherwise experience these courses. College Board agrees, “Since the complete exams are intended to provide the maximum information about differences in student achievement in physics, students may find them more difficult than many classroom exams.” [p. 16, College Board’s AP Physics Course Description.] That's a fancy way of admitting their exam is tough! In fact, just to give a quick statistic, in last year's AP Physics C Mechanics exam, 75 % of students had a raw score lower than 50%. DO NOT let that scare you! I have good news! College Board boasts another statistic, most students who take the exam will score high enough to test out of Physics I in college, 70% of students last year! Admittedly, those are some weird numbers, but trust me, the most important one is that most people pass the test!

That brings me back to the title of the post. All of you are honors students and you either have been or are enrolled in other AP courses, so you know what to expect, but I'm just reminding you of why we work so hard (Spoiler alert: it's because AP Physics is difficult). So in the same breath that I tell you this class is difficult, I will also tell you that it's manageable. The only thing you have to provide is effort. Everything else is provided for you!

-W

Welcome To Willkomm Physics!!!

Ah... The first post of many! The Swedish Chef and I welcome you to the 21st century classroom! Online lessons & assignments are already a mainstay for many university courses, so my goal is to make you all comfortable with this mode of learning. My hope is that this blog will become a classroom outside of the classroom; a place where we can discuss problems from class, homework, or any other physics topics. I look forward to another year of AP and many more posts!