<p>^Yes, we can.</p>
<p>what are you more worried about? MC or free response…</p>
<p>i think MC for me</p>
<p>
</p>
<p>MC because the questions are ********. They’re designed to make you miss them.</p>
<p>MC because you can’t get partial credit, and they’re confusing. like this one:</p>
<p>A heat engine operates in a cycle between temperatures 700 K and 400 K. The heat input to the engine during each cycle is 2800 J. What is the maximum work done by the engine in each cycle?</p>
<p>A) 1200 J
B) 1600 J
C) 2100 J
D) 2800 J
E) 4400 J</p>
<p>I don’t get this question at all!</p>
<p>
</p>
<p>The answer is A.</p>
<p>First, you need to calculate the efficiency of the engine.</p>
<p>Efficiency = (T1 - T2)/T1 = (700 - 400)/700 = .429</p>
<p>You know the heat input is 2800 J, and you know the engine operates with 42.9% efficiency. Therefore, this can be mathematically written as:</p>
<p>.429*2800 = 1200 J</p>
<p>wats Gauge Pressure and the formula 2 find it?</p>
<p>seriously can you guys do the math in your head? I can manage to get them after a while…but some of these questions seem impossible without a calculator…</p>
<p>does anyone know if the Barron’s book is a lot harder than the test?</p>
<p>
</p>
<p>It seems that way at first, but rough everything off. For example, in the problem I just explained, I don’t know what the value of 3/7 is off the top of my head. And because my mental math sucks, I can’t tell you what 2800*3 is in a split second (though if you give me 2 or 3, I could).</p>
<p>But I can tell you that 3000*3 = 9000, and I can rough off 9000/7 to 1200 J.</p>
<p>thanks IRJunkie, but I still probably would’ve skipped that one because it’d take to long to do the math without a calculator. even figuring out how to work your way around not using a calculator takes too much time for me. how does 9000/7 = 1200?</p>
<p>Is the answer 1200 J?</p>
<p>Look at the post I made 1 minute before you posted.</p>
<p>EDIT: Because I don’t want to make yet another post, yes, the answer is 1200 J, DataBox.</p>
<p>yea i see what you mean…but here is a question in the barrons book:</p>
<p>How long will a rock, thrown at a height of 96 m with an initial velocity of 20 meters per second, take to hit the ground?
a) 1 sec
b) 3 sec
c) 5 sec
d) 8 sec
e) 10 sec</p>
<p>They want us to use the quadratic formula and everything…</p>
<p>is this book harder than the test?</p>
<p>the ones with numbers are usually easier because its just plug and play. The conceptual ones screw everyone over.</p>
<p>^ in response to above question</p>
<p>i would take it down to</p>
<p>96=20t+5t^2 and then just try the answers. since we are trying to get 96 it cant be a big number so my mind goes to 3 and 1.</p>
<p>lol IRJunkie beat me to it =)</p>
<p>Physics C is the most difficult AP exam there is</p>
<p>oh ok I get it:</p>
<p>2800 * 3/7 = (2800/7) * 3 = 400 * 3 = 1200</p>
<p>That is a rather convoluted question.</p>
<p>EDIT: Evidently I fail at physics.</p>
<p>wait… is it thrown upwards or downwards???</p>
<p>the answer is B IRjunkie…</p>