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By Callmecollege (Callmecollege) on Wednesday, May 14, 2003 - 06:03 pm: Edit |

http://apcentral.collegeboard.com/repository/ap03_frq_physics_cm_23089.pdf

here are the free response questions from collegeboard, could somebody please help me with question 1, all parts, to see if i did it right, thanx to anyone who contributes!

By Callmecollege (Callmecollege) on Wednesday, May 14, 2003 - 06:11 pm: Edit |

actually, could anyone just tell me any answers that they know for a FACT are correct..all is appreciated

By Brd (Brd) on Thursday, May 15, 2003 - 12:32 am: Edit |

Given: *x(t) = 0.5 t^3 + 2 t*

**(a)** The velocity is *v(t) = dx/dt = 1.5 t^2 + 2*, so at *t=0*, the velocity is *v(0) = 2 m/s*. Speed is the magnitude of velocity, so the speed is also

By Ndhawk (Ndhawk) on Thursday, May 15, 2003 - 12:38 am: Edit |

sweet I got the first completely correct

By Callmecollege (Callmecollege) on Thursday, May 15, 2003 - 12:50 am: Edit |

anymore?

By Eurostar (Eurostar) on Thursday, May 15, 2003 - 06:29 am: Edit |

Yes...FRQ 2. What was the checked box?

By Callmecollege (Callmecollege) on Thursday, May 15, 2003 - 05:57 pm: Edit |

YES, could somebody please help us with the second free response question (spring problem), all parts, i think that that really murdered me and i would like to know the right way to do it

By Brd (Brd) on Friday, May 16, 2003 - 12:00 pm: Edit |

I spend too much time on you guys.

First off, we might as well calculate the spring constant *k*, since it will surely come up, and the problem said to answer only in terms of given quantities and physical constants. Taking *x* to be positive in the "up" direction, the pan is displaced a distance *-D*. At equillibrium the restoring force from the spring exactly balances the force due to gravity on the pan (we assume a massless spring!): *-k*(-D) - Mg = 0*. Solving for *k* yields *k = Mg/D N/m* .

By Callmecollege (Callmecollege) on Friday, May 16, 2003 - 10:09 pm: Edit |

thanks brd!

By Callmecollege (Callmecollege) on Saturday, May 17, 2003 - 12:23 am: Edit |

lucky 3?

By Eurostar (Eurostar) on Saturday, May 17, 2003 - 01:28 pm: Edit |

Thank you so much Brd! So if I got all of the questions in FRQ 1 and FRQ 2 (except for part d)...that would be enough for a 5 right there, right? Considering I did equally on the MC...

By Brd (Brd) on Saturday, May 17, 2003 - 01:57 pm: Edit |

Gosh I am such a pushover. Although, I haven't done problems like this in quite a long while. It's good for me to realize how much I tend to overthink them. Anyways,

Glancing at the problem, it looks like we'll need to calculate the moment of inertia. Since we are assuming a massless bucket, cup and arm, we can just use the formula for point masses: *I = Sum[m_i*r_i^2]*. In our case, we *I = 10(12)^2 + M(2)^2 = 4M +1440*.

**(a)**(i) The data look vaguely proportional to Sqrt[M] (or maybe Log[M]). I imagine this is a gimme question as long as you draw something reasonable.

**(a)**(ii) By hand, I would probably never bother with anything more complicated than linear interpolation. Drawing a straight line between the first two points, you can eyeball a value of about *x ~= 31 m* for

By Brd (Brd) on Saturday, May 17, 2003 - 02:06 pm: Edit |

No problem, Eurostar. I'll be TAing physics classes soon enough; it's good for me to practice explaining problems like these.

By Eurostar (Eurostar) on Saturday, May 17, 2003 - 05:03 pm: Edit |

Wow...so you're a college student, Brd?

By Brd (Brd) on Saturday, May 17, 2003 - 06:21 pm: Edit |

A few times over. I start graduate school in physics in the Fall.

By Miscanon (Miscanon) on Thursday, May 29, 2003 - 05:01 pm: Edit |

I was just reading this...I think I did something completely different for FR # 3 parts b ii. onwards

By Miscanon (Miscanon) on Thursday, May 29, 2003 - 05:03 pm: Edit |

brd...if you have the time can you attempt the E & M problems?

By Miscanon (Miscanon) on Thursday, May 29, 2003 - 05:08 pm: Edit |

okay...I see what I did differently...I forgot to include rotational quantities for part b iii. onwards...now...since c is dependent upon b will they penalize me twice over...or use the ansewr that I put in (b) as the "correct answer"...so I lose points only once? Morever...air resistance is also an answer right brd?

By Miscanon (Miscanon) on Friday, May 30, 2003 - 04:01 pm: Edit |

anyone?

By Miscanon (Miscanon) on Friday, May 30, 2003 - 11:50 pm: Edit |

please....is anyone reading this?

By Brd (Brd) on Saturday, May 31, 2003 - 12:33 am: Edit |

**Miscanon:** If *I* were grading the test, I would say that neglecting air resistance, neglecting losses to internal energy and ignoring the mass of the arm/bucket are all assumptions that would contribute to the model's overestimating the actual measured experimental result. Of course, I'm not grading the thing, but that's what I'd say if I were.

I don't know the answer to your other question about how the later part will be scored.

By Miscanon (Miscanon) on Saturday, May 31, 2003 - 08:58 am: Edit |

Alright, thank you Brd for your response. I appreciate it.

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