<p>anyone know how to do the drawbridge problem? it's the last one on mastering physics</p>
<p>same-only one i cant seem to get</p>
<p>anyone end up getting it?</p>
<p>Just set up the x and y force equations and a torque equation, then solve.</p>
<p>sorry rider730, can you give more details? i dunno bout the rest of you, but im pretty lost on that one…</p>
<p>The key is to get the right diagram for the forces. Tension from the line slanting downward from the high end of the bridge. Weight of the bridge downward from the middle. Normal force from the hinge upward. Last is a reaction force from the hinge directly to the right.</p>
<p>Write the Y force equation, Normal force - mg of the bridge - portion of tension that is downward.</p>
<p>Write the X force equation, the reaction from the hinge - the sideways portion of the tension. </p>
<p>Make the hinge the place where the bridge would rotate and write the torque equation</p>
<p>length of bridge times component of tension acting at 90 degrees to bridge end - half length of bridge times portion of the mg of the bridge that acts at 90 degrees to bridge. </p>
<p>The torque equation has only one unknown, tension, letting you figure out the tension.</p>
<p>Using that and the other two, you can calculate the size of the normal force and the reactive force, which are the two forces that the hinge exerts on the bridge to keep it from translating or rotating. Round them correctly and put them into the F= xx ihat + yy jhat. </p>
<p>Be careful looking at geometry to figure out what trig ratio to use, especially for the tension effect on torque.</p>
<p>Did you three work it out based on that? Any further questions?</p>
<p>went to OH yesterday. lulz. two newtons and one torque orjust use the Tension as found in the first example and put it in to the equations.</p>
<p>dude, Batman. I tried that and I’m still not getting it and only one try left. what was the answer?</p>
<p>nvm-just figured it out :)</p>
<p>Help on number 5 for prelab? And 6 for that matter I guess…</p>
<p>This is the second one of these homework question type threads I’ve seen. This is from the TOS: </p>
<p>“Homework help posts are not allowed - please do your own work, and don’t clutter the forums with requests for other members to do your work for you.”</p>
<p>gaah fine. how about if anyone knows whether we’re gonna have hw over spring break for physics</p>