Simple Dynamics of Circular Motion Problem

From Serway and Jewett Physics for Scientists and Engineers with modern physics, 9th edition


Serway 6.8 problem.jpg

Let’s analyze the wording of the problem:

  1. A conical pendulum is a swinging pendulum that can rotate around an axis. The bob (the mass) will have circular path at all angles θ, but here we need to investigate when the angle is 5°.
  2. When a body moves is circular motion it must have at least a radial acceleration (centripetal acceleration).
  3. The mass is connected by a wire, the wire will have a tension (because it is used to suspend the bob). The tension should have x- and y-components.

What the information give in problem:

  1. The bob’s mass (m) = 80 kg
  2. Length of wire (L) = 10 m
  3. Angle of pendulum (θ) = 5°

What the problem need:

  1. The x- and y-components of tension force.
  2. The radial acceleration



  • The x- and y-components of tension force.
    • The x- and y-components of the tension force are:


  • The radial acceleration

Serway 6.8 problem -sol b.jpg

Author: physicskublog

I teach physics in Kuwait University. I thought of sharing the solutions of selected problems I find in the different Physics 1 and Physics 2 textbooks. I also solve in detail some problems that were given in past exams of Physics 1 and Physics 2. The solutions can help students (and physics enthusiastic) to practice and understand physical concepts better.

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