force: a push or a pull describes why objects move defined by sir isaac newton
TRANSCRIPT
FORCEChapter 4
Force: A push or a pull
Describes why objects move
Defined by Sir Isaac Newton
Newton’s Laws
Newton’s First Law:An object at motion stays in motion unless
acted upon by a net force
In other words: no net force means no change in motion.
Newton’s 2nd Law: F = maMeasured in Newton’s
○ 1 N = 1 kg * m/s2
Newton’s 3rd Law:When an object exerts a force on a second
object, the second exerts a force equal in magnitude but opposite in direction to the first.○ Action-reaction forces
Types of Forces
Gravity: considered to be straight downward.Symbolized Fg or WAlso called Weight
Fg =
Normal Force: force perpendicular to the surface of contact between two surfaces.The force of contact between 2 surfaces.
Net Force
Net force is the sum of all forces acting on an object in a particular direction.
Fnet = mass of object * actual acceleration of the object in that direction
No acceleration means net force = 0 NConstant velocity, object at restEquilibrium
Free-Body Diagrams
Simple sketches that show all forces acting on an object.
You and a friend push a large box across the floor. You push with a force of 100 N, your friend pushes with a force of 85 N. The force of friction on the box is 40 N. The box has a mass of 60 kg. Draw a free body diagram showing all forces acting on the box. Determine the net force acting on the box. What will be the acceleration of the box? How far will the box have moved after 3 seconds?
Finding net force/acceleration
A 14 kg box is being pulled up a ramp inclined at 27 degrees above the horizontal with a force of 140N. The force of friction acting on the box is 35 N. What will be the acceleration of the box?
Homework
Pg. 124 #1-2 Practice A Pg. 128 #1-3 Practice B Pg. 129 #1-5 Section Review
Friction: the force that opposes motion between 2 surfaces.