FORCE: The cause of motion (what causes objects to move) Two types of forces: Push OR a Pull Forces speed things up, slow things down, &/or changes their direction

Measuring Forces SI unit of force is a Newton Symbol: N Measured by using a spring scale

Calculating Net Force If the forces are in the SAME direction, then ____ them! If the forces are in the OPPOSITE directions, then ________ them! ADD SUBTRACT

Balanced or Unbalanced Forces Balanced Forces – all forces acting on an object are equal – There is NO MOTION or CONSTANT MOTION – Subtract the forces and Net Force = 0 – There is NO Acceleration or Deceleration occurring!

Unbalanced Forces – forces are not equal…one or more forces acting on an object is/are stronger than others – There is MOTION – Subtract the forces and a NET FORCE is created that is > 0 – There IS Acceleration or Deceleration occurring!!

Example

PRACTICE! When you subtract the forces, if they = zero, then they are balanced because there is NO net force. In other words, there is NO Acceleration or Deceleration. When you subtract the forces, if they are > 0, then they are unbalanced because there IS a net force. In other words, there IS Acceleration or Deceleration.

1) The skater is not moving. He is on his board getting ready to skate. Net Force = ___ Newtons Balanced or Unbalanced forces? 2) The skater is now moving at a constant rate. He is traveling at 15 mph. Net Force = ___ Newtons Balanced or Unbalanced forces? 3) The skater is pushing his foot along the ground to continue moving. Net Force = ___ Newtons Balanced or Unbalanced forces?

Math In Motion! Force = Mass X Acceleration OR F = M X A measured in N for Newtons – 1 N = 100 grams Momentum = Mass X Velocity measured in kg X m/s (kilograms X meters per second OR mass times velocity units) Speed = Distance ÷ Time measured in m/s (meters per second)

Math In Motion! Velocity = Distance ÷ Time + a Direction (N, S, E, or W) measured in m/s NSEW (meters per second…north, south, east or west) Acceleration = Velocity Final – Velocity Initial ÷ Time measured in m/s/s or ms 2