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## Physics 2211:

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**Physics 2211:**Hooke’s Law Oscillations**If not for elastic forces,**there would be no (living) bungee jumpers . . .**equilibrium length of spring**Experimental Fact: Hooke’s Law**At what time does the block begin to slip?**Block slips when spring force on block exceeds maximum static friction force**At what time does the block begin to slip?**Block slips when spring force on block exceeds maximum static friction force**F**What force F holds the box at rest if it is displaced a distance X?**2nd Newton Law**Try this solution**2nd Newton Law**Try this solution Analogous to circular motion**Problem**A baseball is hit at ground level with an initial velocity of 45 m/s at an angle of 30deg above the horizontal. After achieving its maximum height above ground level the baseball just clears a 10 meter high wall. How far is the wall horizontally from the point where the baseball is hit? (a) 20 m (b) 250 m (c) 160 m (d) 320 m (e) 120 m**problem**Problem 2. An airplane has a cruising speed of 150 mi/h in calm air. The pilot finds that if he sets a compass heading of 10 south of east, it takes him 20 min to fly to a point that is 60 mi due east of his starting point. If east is assumed to be in the positive x direction (and north in the positive y direction), what is the direction of the wind? (a) 39 (b) 54 (c) 49 (d) 44 (e) 30**problem**Problem 3. A mass m attached to the end of a string swings in a vertical circle having a radius of R. At an instant when the string makes an angle of a degrees below the horizontal, the speed of the mass is v. What is the tension in the string at this instant?