Forces in Motion

1
Forces in Motion

• Chapter 13 - Lessons 1 2
• You will discover
• How motion is measured
• How forces affect motion, work, and power

2
How can you describe motion?

• Motion is all around you!
• Types of motion
• Constant steady -
• Vibrational-
• Variable- different directions and speeds -
• Circular -
• Periodic- back and forth -

3
Speed

• Speed describes how far an object moves during a
  certain amount of time.
• Average speed Distance Time
• Speed d t
• Motion is always measured in relationship with
  some location called a point of reference
• Ex Person walking down train car

4
Velocity

• Speed and velocity are not the same
• Velocity describes the speed and direction of a
  moving object
• Ex 30 meters per second north

5
What are forces?

• A force is a push or pull that acts on an object
• Forces can make a moving object slow down, speed
  up, or change direction
• Forces have both magnitude and direction
• Magnitude how strong, measured in newtons (N)
• Direction which way the force is acting, ex
  apple in your hand is exerting a downward force

6
Gravity

• Every object in the universe exerts a
  gravitational pull on every other object
• Earths gravity pulls objects to its center
  without ever touching them
• An objects weight is the amount of gravitational
  force between it and Earth
• Depends on objects mass, Earths mass, how far
  above Earth the object is

7
Magnetism

• A force that pushes and pulls on other objects
• Magnetic force is greatest at poles north and
  south
• Magnets pull strongly on objects made of iron,
  cobalt, nickel, and gadolinium
• Exert forces on other magnets

8
Electricity

• Electric forces act between objects that are
  electrically charged
• Objects get electrically charged when they gain
  or lose electrons
• Gains electrons negatively charged
• Loses electrons positively charged
• Electrons move when objects are rubbed together
• Oppositely charged objects are attracted
• Objects with the same charge repel

9
Gravity, Electricity, Magnetism

• All forces increase as objects get closer
• Magnetism and electricity
• Can be blocked
• Push or pull on objects
• Gravity
• Cannot be blocked
• Pull only

10
Friction

• Force that results when two materials rub against
  each other
• Acts to slow down the motion of an object or keep
  it from starting
• Shape, speed, or texture of object can affect the
  amount of friction w/another object
• Air and water resist motion when a moving object
  pushes against them

11
Work

• Energy used when a force moves an object
• Work Force x Distance
• EX 10N x 2m 20J
• Work is measured in joules
• If the force applied to an object does not make
  it move, no work has been done

12
Power

• The rate at which work is done
• The faster work is done, the more power increases
• Ex Running uphill vs. walking
• Power Work/Time
• Power is measured in watts
• Ex 20J/4s 5W