2. Kinematics 2

3. What’s Most Difficult 05 Right now I am finding remembering stuff from old classes...its too early in the semester =). I took trigonometry last summer and i passed it with flying colors, but then looking at problems, i totally forgot how to do SIN, and COS. Once I look at the problem though it comes to me...it just takes me a while. Otherwise nothing is that difficult right now. =) There are no problems thus far. Im having trouble keeping my thoughts straight on what is velocity and what is acceleration. The problems aren't really all that difficult as of yet. I'm just having trouble getting my brain back in to the swing of things. Finding positive and negative velocities on a graph. telling the difference on a line graph between acceleration and velocity

4. Review Kinematics : Description of Motion –Position –Displacement –Velocity average Instantaneous –Acceleration average instantaneous 07

5. Acceleration Units Speed/time m/s/s = m/s 2 mi/hr/s = mi/hr-s km/hr/s = km/hr-s Distance/time/time or distance/time 2

6. The Ninja The Ninja motorcycle can accelerate from 0 to 60 mi/h in 3.8 s. What is its average acceleration? 15.8 mi/h/s 23 ft/s/s or 7 m/s/s

7. Preflight 4.1 (A) (B)(C) Which x vs t plot shows positive acceleration? 08 86% got this correct!!!! “The slope of the graph is getting increasingly positive; the velocity is increasing over time.”

8. Equations for Constant Acceleration (text, page 34) v = v 0 + at v av = ½ (v o + v) x = x 0 + v 0 t + ½ at 2 v 2 = v 0 2 + 2a(x-x 0 ) 10

9. Kinematics Example A car is traveling 30 m/s and applies its brakes to stop after a distance of 150 m. How fast is the car going after it has traveled ½ the distance (75 meters) ? A) v 15 m/s 18 This tells us v 2 proportional to  x

10. Acceleration ACT An car accelerates uniformly from rest. If it travels a distance D in time t then how far will it travel in a time 2t ? A. D/4 B. D/2 C. D D. 2D E. 4D Correct x=1/2 at 2 Follow up question: If the car has speed v at time t then what is the speed at time 2t ? A. v/4 B. v/2 C. v D. 2v E. 4v Correct v=at 24

11. # 43 Ch 2 A cheetah can accelerate from rest to 25.0 m/s in 6.22 s. Assuming constant acceleration, –A. how far has the cheetah run in this time? –B. after sprinting for just 3.11 s, is the cheetah’s speed 12.5 m/s, > 12.5 m/s, or < 12.5 m/s? –C. what is the cheetah’s average speed for the first 3.11 s? –D. calculate the distance covered by the cheetah in the first 3.11 s.