Free Body Diagrams

1. Free Body Diagrams Newton’s Second Law states that the acceleration of an object is proportional to the net force acting on the object. The Net Force is the vector sum of all the forces acting on the object. A Free Body Diagram is a diagram that shows all of the forces acting on an object, only one object at a time is chosen to show the forces. Separate diagrams are needed if a problem involves more than object is involved in a problem. Include any unknown forces that you have to solve for. Do not show any forces that the chosen object exerts on other objects. Draw the arrow for each force vector reasonably accurately for direction and magnitude. Label each force as to its source. (gravity, friction, object, etc.) In solving the Σ F = ma, resolve vectors into its components. Choose x & y axes that simplifies the calculation.

3. Which is showing the correct FBD for a hockey puck sliding across the frictionless ice?

4. Question 1.  A  group of neighbourhood children play ice hockey. Unfortunately, the rink is on a slope. What forces are acting on the puck?

5. Question 2 The Music Department wants to move a piano up a flight of stairs. The movers tie a rope to the piano, and pull it up a ramp placed over the stairs. The ramp is very smooth (no friction). What forces are acting on the piano?

6. Question 3 Assuming the pendulum in the figure consists of a massive bob hung on a light rope, what forces are acting on the bob?

7. Question 4. You take the elevator to the fourth floor. What forces are acting on you while in the elevator? 

8. Question 5. A pendulum swings in a horizontal circle. What forces are acting on it?

9. Question 6 You push two boxes down the hall over a rough floor. What forces are acting on box A?

10. Question 7. You push two boxes down the hall over a smooth floor (no friction). What forces are acting on box B?

11. Question 8. • A truck accelerates so quickly that a box in front of it does not fall. • What forces are acting on this box?

12. Question 9. Box B accelerates constantly to the right while box A sits on top of it. What forces are acting on box A?

13. Question 10. A physics text and a novel are joined together by a rope as in the figure. What forces are acting on the text if it is sliding down the ramp?

14. Question 11.         A physics text and a novel are joined together by a rope in Figure 1. What forces are acting on the novel if the text is sliding down the ramp?

15. Answers to the Free Body Diagrams 1. C 7. H 2. B 8. G 3. A 9. I 4. E 10. J 5. D 11. F 6. K http://www.physics.uoguelph.ca/tutorials/fbd/Qmenu.htm