5.2.9

Free Body Force Diagrams

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Free Body Force Diagram

A free body force diagram is a diagram showing the forces acting on an object. These are shown as vectors.

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Skydiver

  • The forces acting on a skydiver are air resistance (acting upwards) and the skydiver’s weight (acting downwards).
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Driving car

  • The forces acting on a driving car are the driving force, the normal contact force, the weight and friction.

Free Body Diagram - Uses

We can use free body diagrams to work out the resultant force when more than one force is acting on an object. We can also use the diagrams to see if an object is in equilibrium. If the resultant force is zero, we say the object is in equilibrium.

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Accelerating car

Here are the forces acting on an accelerating car:

  • Resultant force upwards = 5000 N - 5000 N = 0 N
  • Resultant force forwards = 3000 N - 1000 N = 2000 N
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Car at a steady speed

If the driving force is reduced to 1000 N, the car is in equilibrium.

  • Resultant force upwards = 5000 N - 5000 N = 0 N
  • Resultant force left = 1000 N - 1000 N = 0 N

Jump to other topics

1Energy

2Electricity

3Particle Model of Matter

4Atoms & Radiation

5Forces

5.1Basics of Motion

5.2Forces

5.3Effects of Forces

5.4Pressure

6Waves

7Magnetism

8Astrophysics

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