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Showing posts from November, 2012

### Projectile Motion : Practice Problems + Solutions

Solve the following questions using what you know about projectile motion.
1.A roadrunner runs directly off a cliff with an initial velocity of 3.5 m/s. a)What are the components of this velocity? Vx = 3.5 m/s                            Vy = 0 m/s
b)What will be the horizontal velocity 2 seconds after the bird leaves the cliff? 3.5 m/s – horizontal velocity is unchanging
c)If the cliff is 300 m high, at what time will the roadrunner reach the ground? h = dy = ½ * 10 * t2 = 300 300 * 2 / 10 = t2 = 60 t = 7.75 s
d)How far from the cliff will this bird land? dx = 3.5 * 7.75 = 27.125 m
e)If there is a small pond which begins 25m away from the cliff and extends 2.5 meters from there; will the roadrunner land in the pond? Yes, the pond is from 25 m to 27.5 m, so the roadrunner will land in the pond.
f)What is the final vertical velocity at which the roadrunner is traveling? [The vertical velocity at the time when the bird reaches the ground] Vy = 10 * 7.75 + 0 = 77.5 m/s
g)What is the final horizontal vel…

### Chapter 6: Work and Energy

Practice Problems

1Just as a car tops a 38 meter high hill with a speed of 80 km/h it runs out of gas and coasts from there, without friction or drag. How high, to the nearest meter, will the car coast up the next hill?
2A pendulum has a mass of 3.6 kg, a length of 1.7 meters, and swings through a (half)arc of 29.4 degrees. What is its amplitude to the nearest centimeter?
3To the nearest tenth of a Joule, what is its maximum kinetic energy of the pendulum in problem 2?
4To the nearest tenth of a Joule, what is the total energy of the pendulum in problem 2?
5A 2 kg metal plate slides down a 13-meter high slope. At the bottom its speed is 9 m/s. To the nearest Joule, what was the magnitude of the work done by friction?
6If the slope in the above problem is 23 degrees, what is the coefficent of friction (to 2 decimal places)?
7An unstretched spring with spring constant 36 N/cm is suspended from the ceiling. A 3.6 kg mass is attached to the spring and let fall. To the nearest tenth of a c…