Forces

Forces

• 1.
  Forces
• 2.
  What is aforce?  A force is a push or pull from one object to another object  Examples: Earth’s gravitational pull on us, you pushing a chair, a table supporting a book
• 3.
  What is aforce?  All forces have both size and direction  The unit of force is the Newton (N)  What other concepts have both a size and direction?
• 4.
  Net Forces  The net force is the combination all of the forces acting on the object  Whenever more than one force act on an object, always sum the forces into a single net force
• 5.
  Forces in theSame Direction  When forces act in the same direction, you add the forces together  The net force will be in the same direction as the two original forces F1= 5 N Fnet= 8 N F2= 3 N
• 6.
  Forces in theOpposite Direction  When two forces act in opposite directions, you subtract the smaller force from the larger force  The net force will be in the direction of the larger force F1= 2 N F2= 7 N Fnet= 5 N
• 7.
  Balanced Forces  When the sum of the forces acting on an object equals zero, the forces are said to be balanced.  Balanced forces are equal in size and opposite in direction
• 8.
  Balanced Forces- Newton’s1st Law  There is no change in motion when the forces are balanced.  A stationary object remains stationary  A moving object has constant velocity
• 9.
  Unbalanced Forces  When the sum of the forces are non- zero, there are unbalanced forces acting on the object  Unbalanced forces produce a change in motion, so they are necessary to cause accelerated motion
• 10.
  The Big Idea  Unbalanced forces result in a net force  The net force causes the object to accelerate  This acceleration can be predicted and described
• 11.
  Force, Mass, and Acceleration  An object accelerates when a net force acts upon it  The net force is equal to the mass times the acceleration: F = ma  This relationship is Newton’s 2nd Law
• 12.
  Force, Mass, and Acceleration  The acceleration of the object depends on both the forces acting on the object and the mass of the object  The net force and acceleration are always in the same direction!! F1= 2 N F2= 7 N Fnet= 5 N a
• 13.
  Example 1  How much force is needed to accelerate a 30 kg scooter at a rate of 1 m/s2? F = ma F = (30 kg) x (1m/s2) F = 30 N
• 14.
  Example 2  How much force is needed to accelerate a 0.5 kg baseball at a rate of 0.04 m/s2? F = ma F = (0.5 kg) x (0.04 m/s2) F = 0.2 N