Chapter 1 Forces and Pressure

1
Chapter 1Forces and Pressure

• Section 1-2
• How Forces Act on Objects

2
I. Newtons Second Law of Motion

• The force on an object equals the mass of the
  object times the acceleration of the object.
• F MA
• Ex. F 10kg x 2 m/s2
• F 20N

3

• F 100N A 20 m/s2 M ?
• F MA
• 100N 20 m/s2 x M
• 100N 20 m/s2 M
• M 5 kg

4

• Units of Force
• Mass is measured in kg
• Acceleration is measured in m/s2
• Unit of Force kilograms x meter/second2
  (kg/m/s2)
• Labeled as N

5

• Newton (N)
• The metric measurement of force.
• In the English system, force is measured in
  pounds

6
II. Balanced Forces

• Forces acting on an object cancel each other.
  They are equal
• There is NO acceleration

7
III. Unbalanced Forces and Acceleration

• Objects accelerate only when they are acted on by
  an unbalanced force.

8
IV. Centripetal Force

• Force exerted to keep an object moving in a
  circle
• There is constant acceleration toward the center
  of the circle

9
V. Weight as Force

• Force of gravity accelerates mass downward 9.8 N.
• Gravitational Force is 9.8 m/s2
• If you jump off a mountain, you will accelerate
  downward at the rate of 9.8 m/s2

10

• The gravitational force on you or any object is
  called weight
• Weight is found by multiplying the acceleration
  due to gravity times the mass of the object (F
  MA)

11
VI. Action and Reaction Forces

• Action Force.
• Force when you push on something
• Reaction Force
• The force that pushes back on you at the same
  moment as the action force
• Action/Reaction Forces always occur in pairs.

12
VII. Newtons Third Law

• For every action there is an equal and opposite
  reaction
• These forces always occur together.