<p>join guys 10char</p>
<p>going over physics 1993 mc test currently</p>
<p>keepin this thread alive</p>
<p>btw if anyone has the 2008 free response questions form A and B could they send it to me? the ap central site to download those are down :(. my email is <a href="mailto:megatw1412■■■■■■.com">megatw1412■■■■■■.com</a></p>
<p>edit: nvm, collegeboard is back up and running again</p>
<p>Two cars travel along a level highway in the same direction. It is observed that the distance between the cars is increasing. Which one of the following statements concerning this situation is necessarily true?
(a) The velocity of each car is increasing.
(b) At least one of the cars has a non-zero acceleration.
(c) The leading car has the greater acceleration.
(d) The trailing car has the smaller acceleration.
(e) Both cars could be accelerating at the same rate.</p>
<p>^ Should be (b) shouldn’t it?</p>
<p>(a) is wrong because the one could have constant velocity, the other positive acceleration
(c) is wrong because couldn’t the trailing car just be slowing down/negative acceleration?
(d) I’m not sure about, because I’m iffy on what “greater acceleration” means; couldn’t it mean a higher acceleration but in the opposite direction?
(e) same rate of acceleration produces same speed, doesn’t it</p>
<p>correct answer is e :(</p>
<p>A boat that can travel at 4.0 km/h in still water crosses a river with a current of 2.0 km/h. At what angle must the boat be pointed upstream (that is, relative to its actual path) to go straight across the river?
(a) 27° (c) 60° (e) 90°
(b) 30° (d) 63°</p>
<p>^I don’t think you gave us enough information. We also need the direction of the current relative to the boat.</p>
<p>Of course it’s e.
a) nope. they could be not increasing, but one car has higher initial velocity
b) nope. both could be accelerating, one is just faster.
c) could both have no acceleration but traveling in opposite directions
d) same thing
e) both cars COULD be accelerating at same rate, but one has higher initial, or traveling opposite directions</p>
<p>b) 30 degrees</p>
<p>And yes, the answer to the previous question is most definitely (e), (b) is incorrect as the condition does not guarantee acceleration (leading car could have an acceleration of 0 m/s/s and velocity of 50 m/s, while the lagging car could have an acceleration of 1 m/s/s and velocity of 5 m/s; in this case, the lagging car has the greater acceleration, yet the distance between the vehicles is still increasing)</p>
<p>jzhang722, how did u get 30 degrees? thats the correct answer btw 
</p>
<p>and can any1 explain why (e) right for the previous qs? I am still unclear</p>
<p>and the cars are traveling in the same direction same direction jzhang</p>
<p>everyone back on the chatroom</p>
<p>Yeah, jzhang, could you explain you answer to the boat question?</p>
<p>I got 27 degrees but i had to use law of cosine. :S</p>
<p>I think I see why it’s 30°. This is just a fancied-up vector problem. A vector of 2 in the horizontal direction [to the right, I guess], so the 4 of the boat must produce a horizontal vector of 2 in the opposite direction [to the left, in this case].</p>
<p>It’s asking for the angle the boat should make to its regular, straight path across the river. So if it makes a 30° angle with that path, it makes a triangle with hypotenuse 4 and horizontal component 2, since the actual angle is 60°. </p>
<p>Pretty bad explanation, so here’s a little MS Paint:</p>
<p><a href=“ImageShack - Best place for all of your image hosting and image sharing needs”>ImageShack - Best place for all of your image hosting and image sharing needs;
<p>So can someone explain the relationship between thermal energy, heat, and temperature? [Not a quiz question; I actually don’t understand this]</p>
<p>I can’t wait to make love to the Physics B exam :)</p>
<p>An apple crate with a weight of 225 N accelerates along a frictionless surface as the crate is pulled with a force of 14.5 N as shown in the drawing. What is the horizontal acceleration of the crate?</p>
<p>and show ur work plz</p>