homework02

# homework02 - PHYS 121 Homework 2 Due 29 January 2007...

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PHYS 121 Homework 2 Due: 29 January 2007 Problem 1. (i) Consider two arbitrary non-zero vectors ±a and ± b and a third vector constructed from the diﬀerence of them, ± c = ±a - ± b . State whether the following statements can be true or not and brieﬂy justify your answers: (1) c > a , (2) c > a and c > b , (3) c = a + b , and (4) c > a + b . [ Note : Recall that c ≡ | ± c | .] (ii) You throw a ball upward at some angle. After some time you measure the velocity of the ball to be ±v = (15ˆ ı - 2 . ) m / s. Did you measure the velocity when the ball was on the way up or the way down? [ Note : Assume the standard coordinate system where x is positive to the right and y is positive upward.] (iii) Question 4.3. (iv) A projectile is launched with an initial velocity, ±v 0 = v 0 ,x ˆ ı + v 0 ,y ˆ . What is the velocity of the projectile when it reaches the top of its trajectory, ±v top ? What is the acceleration of the projectile when it reaches the top of its trajectory, ±a top ? (v) Is it possible to accelerate while moving at a constant speed? (vi) Is it possible to accelerate while moving at a constant velocity? Problem 2. (i) Problem 3.4. (ii) A vector has a magnitude of 8 . 0 m and points at 130 as measured from the x -axis. Write this vector in unit vector notation. Problem 3.

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homework02 - PHYS 121 Homework 2 Due 29 January 2007...

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