forces in 1 dimension chapter 4. 4.1 force and motion force is push or pull exerted on object forces...
TRANSCRIPT
Forces in 1 Dimension
Chapter 4
4.1 Force and Motion• Force is push or pull exerted on object• Forces change motion
– Makes it important to know the forces on an object
• Force diagrams (free body diagrams) show all forces acting on object– Both direction and magnitude – vector– Define system
Contact and Field Forces• Contact – touching• Field – non-contact
(not touching)
• Every touch generates force
• Table 4-2, pg 94
Force and Acceleration• Forces change motion• Newton’s 2nd Law
– a = Fnet/m
– Net forces and mass will affect the acceleration of an object• Applying a force changes the object’s motion –
generates an acceleration• Changing mass, changes forces
Newton’s 1st Law• “An object that is at rest will remain at rest,
and an object that is moving will continue to move in a straight line with constant speed, if and only if the net force acting on that object is zero”
• Inertia – tendency of an object to resist change– Not a force
• Equilibrium – net force on object is zero
4.2 Using Newton’s Laws• Weight – gravitational force acting on object
– Changes depending on where you are in Universe
• Scales – How it Works, pg 110• Apparent weight – weight changes with
motion– Example: elevator– Weightlessness – apparent weight is zero
• No contact forces pushing up on object
Drag Force• Particles of air exert forces on an object
– Often is a huge force• Drag force – force exerted by a fluid on an
object moving through the fluid– Direct relationship – increase speed, increase
drag force– Affected by size and shape of object, and
temperature and viscosity of fluid
Terminal Velocity
• Constant velocity is reached when drag force equals gravitational force
4.3 Interaction Forces• Interaction pairs• Newton’s 3rd Law states that all forces come
in pairs– One doesn’t cause the other– Because there is one, there is the other– Equal in magnitude and opposite in direction– 2 force diagrams – each one contains one of the
forces in the interaction pair
The Normal Force• Support force• Perpendicular
contact force exerted by a surface on another object
Lab• Force table lab• Newton’s second lab