Forces and Free Body Diagrams

​Net Force and Free Body Diagrams

What are they and how do we use them? ​

When we push or pull ​on an object, we apply a force to that object.

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Forces Cause Masses to Accelerate​

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1. Force of Gravity

2. Normal Force

3. Applied Force

4. Friction force

5. etc...​

​Different Types of Forces

​A Net force is the resulting force from adding together all forces acting on an object

Net Forces​

​Different kinds of Forces

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Multiple Choice

What is the Net force is this example?

• - 100 N

• + 100 N

• 400 N

• 300 N

Fill in the Blank

WHY?

​Force of gravity pulling an object down towards the center of the earth (Always straight down)

​​Gravity

​"Normal" to any surface an object sits on. The force of the table pushing back on the object

​​Normal

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​Force of me pushing/ pulling on an object. What force is being applied to the object?

​​Applied

Force opposing the motion of the object. The more Normal Force, the stronger the friction

​​Friction

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Picture of all the forces acting on an object at once. ​

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​Free Body Diagram

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Multiple Choice

What is the Net force on this object likely to be?

• 0, All forces are equal and opposite

• In the direction of the friction force

• Off the table in the direction of the normal force

• Down the ramp in the direction of the applied force

Often times 2D forces have components

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(Normally the force of gravity)​

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​Forces have components too!

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Multiple Choice

What force will always be equal and opposite to the Vertical Component of Gravity in this picture?

• Friction force

• Force of gravity

• Normal force

• Horizontal gravity component

​Objects that have constant velocity don't have a net force being applied to them. For example, if a hockey puck is pushed on a rink and sliding on the ice with no friction, it will keep moving in the same direction until another force acts on it.

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​Objects with Constant Velocity