<li><p>A rope of length 15 m is stretched to a tension of 6 N. A 3 Hz wave travels down the rope in 5 s. What is the mass of the rope?</p></li>
<li><p>What is the frequency of the beats if a tuning fork of frequency 400 Hz and a tuning fork of frequency 396 Hz are simultaneously disturbed by a force?</p></li>
<li><p>A biconcave lens has a focal length of 20 cm. How far is it from an object placed 30 cm from the lens to its image formed by the lens? (I don’t understand what the problem is asking for).</p></li>
<li><p>Which of the following best explains why the diffraction of sound is in general more evident than the diffraction of light?</p></li>
</ol>
<p>(A) Light waves are transverse and sound waves are longitudinal.
(B) Light waves have smaller wavelengths than sound waves
(C) Ligh travels at a much faster velocity than sound.
(D) Light can propagate through empty space, sound can not.
(E) Light waves can be polarized, sound can not.</p>
<p>I figured out the answer to the 2nd and 4th one. Can someone help me with #868 and #1056?</p>
<p>wow.. this seems hard.. sorry I have no idea how to solve them..</p>
<p>is this for AP Physics B or C?</p>
<p>don't feel like lookin up the first one.</p>
<p>3rd one- you're given a focal length (20 cm), you're given a di(?) of 30 cm, solve for do(?)</p>
<p>either that or you're given do and u gotta solve for di, or solve for the distance from the object to the image or somethin....... not sure.</p>
<p>For the first one, v=sqrt(Tension/mu) where mu is the linear mass density.</p>
<p>mu=T/v^2</p>
<p>Thus, m=l*T/v^2</p>
<p>I'll let you do the calculations.</p>
<p>1056: 1/distance object (do) + 1/ distance image (di) = 1/f (focal length). It is asking for the combined distance from the object to the mirror and the mirror to the image</p>
<p>Using the lengths given (f = 20; do = 30) 1/30 + 1/di = 1/20; 1/di = 1/20-1/30 = 1/60. Therefore, di = 60cm. So the TOTAL distance from the object to the image is 30cm + 60cm = 90 cm or 0.9m</p>
<p>868: sorry, I used to know the formula (did at beginning of year) but I forgot. Hopefully someone else can help you. Good luck.</p>