Uniform Acceleration

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Uniform Acceleration

• By Eli Jaggard
• For use with The Physical World Lab

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Table of Contents
Uniform Acceleration

• What is Gravity?
• Gravity versus Air Resistance
• Feather/Hammer Drop on Earth
• Feather/Hammer Drop on Moon
• Gravity versus Horizontal Motion

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What is Gravity?
Uniform Acceleration

• Gravity is a force of attraction only between
  bodies that have mass. The word 'gravity' comes
  from the Latin word "gravitas," meaning 'weight.

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What is Gravity?

• The acceleration produced in the body on
  account of the force of gravity is called
  acceleration due to gravity. It is denoted by the
  letter g.

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What is Gravity?

• At a given place, the value of acceleration
  due to gravity is the same for all bodies
  regardless of their masses, density or shape.
  However, it differs from place to place on the
  surface of earth and it also varies with altitude
  and depth.

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Gravity versus Air Resistance

• Many people find it hard to believe that if
  they drop a feather and a hammer at the same
  time, the two should hit the ground at the same
  time. On Earth the hammer will always strike the
  ground first.

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Gravity versus Air Resistance

• This is because the hammer has less air
  resistance than does the feather. The reason the
  hammer hits first is because Earth has an
  atmosphere, not because the hammer is heavier!

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Feather/Hammer Drop on Earth

• As you already know, on Earth the hammer will
  hit the ground first

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Feather/Hammer Drop on Moon

• But, in the absence of an atmosphere, the two
  will hit at the same time!

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Gravity versus Horizontal Motion

• When an object has motion both vertically and
  horizontally, it is said to have a projectile
  motion.

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Gravity versus Horizontal Motion

• In projectile motion, the horizontal motion and
  the vertical motion are independent of each
  other that is, neither motion affects the other.

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Gravity versus Horizontal Motion

• Consider the two balls. The fact that one ball is
  moving horizontally while it is falling has no
  effect on its vertical motion.