CT2-1CT2-2 CT2-3CT2-4 CT2-5CT2-6CT2-7CT2-8CT2-9CT2-10 A student sees the following question on his CAPA assignment due Friday night at 10 pm: A ball is thrown vertically upwards with an initial velocity of 21.62 m/s. Neglecting air resistance, what is the greatest height reached by the ball?Which of the following formulas should the student use to answer the question?A) ov v a t= +B)2o ox x v t (1/ 2) a t= + +C)2 2o ov v 2a (x x )= + -D)ov vv2+=Answer: (C) The statement of the problem gives vo, vfinal = v = 0, and a = g. We see the position. Equation C relates all these quantities. A) and B) are not as useful as C) because we don't know the time t.CT2-11 A ball is thrown straight upward. At the top of its trajectory, its acceleration is..A: zero B: straight up C: straight down D: depends on the mass of the ballAnswer: straight down. The acceleration due to gravity is always straight down, regardless of the velocity of the ball.CT2-12 A rock is dropped from rest and falls a distanceh (h > 0 ) to the ground. Down is chosen as the positivedirection and the origin is placed at ground level.What is y0 (the initial position) and what is a (theacceleration)?A) y0 = +h , a = – gB) y0 = –h , a = + g C) y0 = 0 , a = + g D) y0 = – h , a = – g E) y0 = 0 , a = – g+y0hv0 = 0Answer: y0 = –h , a = + g (yfinal = 0)CT2-13 If you drop an object in the absence of air resistance, it accelerates downward at 9.8m/s2. If instead you throw it downward, its downward acceleration after release is….A: less than 9.8m/s2. B: 9.8m/s2C: more than 9.8m/s2.Answer: 9.8 m/s2 The acceleration due to gravity is always straight down, always has magnitude g , regardless of the velocity of the object.CT2-14 An object's velocity vs. time graph looks like this:What situation produces this kind of motion?A) A rock is thrown straight up. B) A rock is dropped from rest.C) A rock is thrown straight down. D) A book slides along a table and comes to restE) None of these.Answer: A rock is thrown straight up.vtCT2-15 On planet X, a cannon ball is fired straight upward. The position and velocity of the ball at many times are listed below. Note that we have chosen up as the positive direction.Time(s) Height(m) Velocity(m/s)0 0 201 17.5 152 30 103 37.5 54 40 05 37.5 -56 30 -107 17.5 -158 0 -20What is the acceleration due to gravity on Planet X?A: –5m/s2B: –10m/s2C: –15m/s2D: –20m/s2E: None of these.Answer: –5m/s2 Use a = (v2 – v1)/(t2 – t1) and then use any pair of points from the table.CT2-15A ball is fired from a canon straight upward with an initial velocity vo. Assume no air resistance. If the initial velocity vo is doubled, the time to reach the apex of the trajectory..A: doubles. B: increases by a factor of 4. C: Neither of these.D: Impossible to tell from the information given.Answer: In lecture we derived the formula for the time to reach the apex: t = v0 / g. If v0 is doubled, then t doubles.If the initial velocity vo is doubled, the maximum height of the ball..A: doubles. B: increases by a factor of 4. C: Neither of these.D: Impossible to tell from the information given.Answer: In lecture we derived the formula for the max height of the ball :y = v02 / (2g). Ifv0 is doubled, then y increases by a factor of 4.yCT2-17 The distance x traveled by a ball in a time t is given by the formula21x a t2=where a is a non-zero positive constant. What happens to the distance x when the time t is tripled?A) x increases by a factor of 3 B) x increases by a factor of 9/2C) x increases by a factor of 9 D) x increases by a factor that depends on the value of aAnswer: x increases by a factor of 9 =