131_PartUniversity Physics Solution

131_PartUniversity Physics Solution - Applying Newtons Laws...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Applying Newton°s Laws 5-3 5.6. I DENTIFY : Apply Newton°s 1st law to the car. The forces are the same as in Example 5.5. S ET U P : The free-body diagram is sketched in Figure 5.6. E XECUTE : x x F ma = cos sin 0 T n α α = cos sin T n α α = y y F ma = cos sin 0 n T w α α + = cos sin n T w α α + = Figure 5.6 The first equation gives cos . sin n T α α = Use this in the second equation to eliminate n : cos cos sin sin T T w α α α α + = Multiply this equation by sin : α 2 2 (cos sin ) sin T w α α α + = sin T w α = (since 2 2 cos sin 1 α α + = ). Then cos cos sin cos . sin sin n T w w α α α α α α = = = E VALUATE : These results are the same as obtained in Example 5.5. The choice of coordinate axes is up to us. Some choices may make the calculation easier, but the results are the same for any choice of axes. 5.7. I DENTIFY : Apply m = F a ! ! to the car. S ET U P : Use coordinates with x + parallel to the surface of the street. E XECUTE : 0 x F = gives sin T w α = . 2 3 sin (1390 kg)(9.80 m/s )sin17.5 4.10 10 N F mg θ = = ° = × . E VALUATE : The force required is less than the weight of the car by the factor sin α . 5.8. I DENTIFY : Apply Newton°s 1st law to the wrecking ball. Each cable exerts a force on the ball, directed along the cable. S ET U P : The force diagram for the wrecking ball is sketched in Figure 5.8. Figure 5.8 E XECUTE : (a) y y F ma = cos40 0 B T mg ° − = 2 4 (4090 kg)(9.80 m/s ) 5.23 10 N cos40 cos40 B mg T = = = × ° ° (b) x x F ma = sin40 0 B A T T ° − = 4 sin40 3.36 10 N A B T T = ° = × E VALUATE : If the angle 40 ° is replaces by 0 ° (cable B is vertical), then B T mg = and 0. A T =
Image of page 1

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

View Full Document Right Arrow Icon
5-4 Chapter 5 5.9. I DENTIFY : Apply m = F a ! ! to the object and to the knot where the cords are joined. S ET U P : Let y + be upward and x + be to the right.
Image of page 2
Image of page 3
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