{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

HW2 solutions - HomeWork 2 solutions 1 Cutnell Johnson 8th...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
HomeWork 2 solutions Physics 203 1. Cutnell & Johnson 8 th Edition, Chapter 2, Problem 67 REASONING The slope of a straight-line segment in a position-versus-time graph is the average velocity. The algebraic sign of the average velocity, therefore, corresponds to the sign of the slope. SOLUTION a. The slope, and hence the average velocity, is positive for segments A and C , negative for segment B , and zero for segment D . b. In the given position-versus-time graph, we find the slopes of the four straight-line segments to be 1.25 km 0 km 6.3 km/h 0.20 h 0 h 0.50 km 1.25 km 3.8 km/h 0.40 h 0.20 h 0.75 km 0.50 km 0.63 km/h 0.80 h 0.40 h 0.75 km 0.75 km 0 km/h 1.00 h 0.80 h A B C D v v v v = = + = = = = + = = 2. Problem 39. Add “during this time” to the end of the last sentence. REASONING Because the car is traveling in the + x direction and decelerating, its acceleration is negative: a = −2.70 m/s 2 . The final velocity for the interval is given ( v = +4.50 m/s), as well as the elapsed time ( t = 3.00 s). Both the car’s displacement x and its initial velocity v 0 at the instant braking begins are unknown. Compare the list of known kinematic quantities ( v , a , t ) to the equations of kinematics for constant acceleration: 0 v v at = + (Equation 2.4), ( ) 1 0 2 x v v t = (Equation 2.7), 2 1 0 2 x v t at = + (Equation 2.8), and 2 2 0 2 v v ax = + (Equation 2.9). None of these four equations contains all three known quantities and the desired displacement x , and each of them contains the initial velocity v 0 . Since the initial velocity is neither known nor requested, we can combine two kinematic equations to eliminate it, leaving an equation in which x is the only unknown quantity.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern