Introduction to Forces Part 1

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Introduction to ForcesPart 1

• What is a force?
• What does it do?
• What kind of forces exist in the universe?

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Objectives

• 12.1.1) Describe a force and explain its effects
  on the motion of an object
• 12.1.2) Explain the similarities and differences
  between contact forces and field forces

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Objectives

• 12.1.3) State the SI unit for force
• 12.4.1) State and describe the four kinds of
  forces that exist in the universe, including
• Relative strength
• How far does the force act

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What is a force?

• A push or pull on an object
• Forces cause acceleration
• Forces cause objects to
• Speed up
• Slow down
• Change directions

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What is a force?

• Forces are vector quantities
• They have
• magnitude (how big is the force?)
• direction (which way is the force acting?)
• Forces are represented by arrows where the length
  represents how big the force is

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How do forces work?

• Contact Force changes the motion of an object by
  physical contact
• Pushes, pulls, friction
• Field Force changes the motion of an object
  without actually touching it
• Gravity, Magnets, /- charges

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How do forces work?
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Measuring Force

• Forces are measured in Newtons (N)
• 1 N is the force required to cause an
  acceleration of 1 m/s2 on a 1 kg object
• Apple to your mouth

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Measuring Force
0 m/s
00001
1 m/s
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Types of Forces

• Electromagnetic Forces
• Forces between charged particles (positive and/or
  negative charges)
• Only forces that can both attract (opposite
  charges) and repel (like charges)
• Ex Protons/Neutrons Magnets

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Electromagnetic Forces
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Types of Forces

• Strong Nuclear Force
• Force of attraction that acts on protons and
  neutrons in the nucleus of an atom, holding them
  together
• Very strong force that acts over very short
  distances
• 10-15 m (the diameter of one proton)

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Types of Forces

• Weak Nuclear Force
• Attractive force that acts on all particles in an
  atom, not just protons and neutrons
• Weaker than the strong nuclear force and does not
  act as far as strong nuclear force

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Types of Forces

• Gravity
• Attractive force between any two masses in the
  universe
• Gravity is the weakest force, but acts over the
  longest distances

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Types of Forces

• The greater the mass of the objects, the greater
  the gravitational force between them
• As distance between two objects increases,
  gravitational force decreases