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FRICTIO FRICTIONAL FORCES. Free body diagram: A book lying on a level table.

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Presentation on theme: "FRICTIO FRICTIONAL FORCES. Free body diagram: A book lying on a level table."— Presentation transcript:

1 FRICTIO FRICTIONAL FORCES

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3 Free body diagram: A book lying on a level table

4 Free body diagram: A person floating in still water

5 Free body diagram: A wrecking ball hanging vertically from a cable

6 Free body diagram: A helicopter hovering in place

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9 3 Free Body Diagrams: Move R, accel R Move R, no accel Move R, accel L

10 Free Body Diagrams Notes

11 newtonN, newton, - N, unit of force in the metric systemforcemetric system - force needed to push a 1kg object at a speed of 1m/s for a second. mass, mass, in physics, the quantity of matter in a body regardless of its volume or of any forces acting on it. weight, weight, measure of the force of gravity on a body Key Terms

12 Weight (W) Weight (W) varies depending upon the location of the body in the earth's gravitational field (or the gravitational field of some other astronomical body). The acceleration of gravity on earth is approximately: 9.8 m/s² in SI units and 32 ft/s² in US Customary units. weight massacceleration of gravity. To calculate the weight of an object you have to multiply it’s mass times the acceleration of gravity. W= m *g W = m * g What does gravity have to do with the weight of an object?

13 W = m * g Write the formula: Substitute known values: Present solution with units: W = (225,000 kg) * 9.8 m/s² W = ,200,000 N weight massacceleration of gravity. To calculate the weight of an object you have to multiply it’s mass times the acceleration of gravity. What the heck is 2,200,000 N? The Statue of Liberty has a mass of 225,000 kg. How much does she weigh? The Statue of Liberty weighs 2,207,250 Newtons, which is 495,000 lbs pounds!

14 This is a free-body diagram of the Statue of Liberty. She is represented by a simple box. The forces acting on her are labeled with a magnitude and the arrow shows direction. Notice the surrounding objects are stripped away and the forces acting on the object are shown lb free-body diagram A free-body diagram illustrates the relative magnitude and direction of all forces acting upon an object. The object must be isolated and “free” of its surroundings.

15 “FW” here represents the force of the weight of the statue. “FN” is the normal force, which represents the force Liberty Island is pushing back up on the statue. 495,000 lb F N = F W = The island has a great resistance to compression. The ground is exerting a force upward on the statue perpendicular, or normal, to the surface. Normal: means perpendicular to, (ex. The walls to the floor) The force of the pedestal to the statue is normal to the surface of the ground.

16 Think of the diagram on an XY plane. If “up” is assumed to be the positive direction, then N is positive and W is negative. -495,000 lb 495,000 lb FN = FW = (Positive y-direction) +y +x (Positive x-direction) When forces acting on the object cancel each other out it is in a state of static equilibrium.

17 Create a free body diagram (FBD) of the gorilla: Sitting Gorilla Free Body Diagram of the Sitting Gorilla (The box represents the gorilla, W = weight of the gorilla, N = Normal force) FWFW Gorilla FNFN

18 Parrot on wooden swing hung by ropes Draw a FBD of the wooden swing: Swing Free Body Diagram of the wooden swing (The box represents the wooden swing, W = weight of the swing and the parrot, T represents the ropes that are in tension supporting the weight) FWFW F T2 F T1 Where are the forces on the swing?

19 Bungee jumping from crane Draw a FBD of bucket the bungee jumper leaped from: Free Body Diagram of the bucket (T represents the tensile force of the cable the bucket is suspended from, and W is the weight of the diver and the bucket) FWFW FTFT bucket Where are the forces on the bucket?

20 Traffic Light supported by cables Draw a FBD of the ring at point C: A B C D Free Body Diagram of the ring at point C (T represents the force of the cables that are in tension acting on the ring) F TCA F TCD F TCB Where are the forces on the ring?

21 Draw a FBD of the traffic light: Free Body Diagram of the traffic light (F TCD represents the force of the cables acting on the light and F W is the weight acting on the light) FWFW F TCD Light Traffic Light supported by cables A B C D Where are the forces on the light?

22 Pin-Connected Pratt Through Truss Bridge Draw a FBD of the pin at point A: A B E D C Free Body Diagram of pin A (If you consider the third dimension, then there is an additional force acting on point A into the paper: The force of the beam that connects the front of the bridge to the back of the bridge.) F TAE F TAC F TAB F TAD Where are the forces on point A?

23 Sitting Gorilla

24 Parrot on wooden swing hung by ropes Draw a FBD of the wooden swing: Where are the forces on the swing?

25 Bungee jumping from crane Draw a FBD of bucket the bungee jumper leaped from: Where are the forces on the bucket?

26 Traffic Light supported by cables Draw a FBD of the ring at point C: A B C D Where are the forces on the ring?

27 Draw a FBD of the traffic light: Traffic Light supported by cables A B C D Where are the forces on the light?

28 Pin-Connected Pratt Through Truss Bridge Draw a FBD of the pin at point A: A B E D C Where are the forces on point A?


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