Presentation on theme: "Chapter 12: Forces and Motion"— Presentation transcript:
1 Chapter 12: Forces and Motion Section 12.1Forces
2 Forces A push or pull that acts on an object Can cause an object to start moving or it can change an object’s accelerationMeasured in Newtons (N)Force is a vector ~ shows direction and magnitudeNet force is the overall force acting on an object after all forces have been combined.
3 Balanced and Unbalanced Forces Balanced forces combine to form a net force of 0.There is no change in the object’s motion.Unbalanced forces combine to form a net force not equal to 0.Unbalanced forces cause objects to accelerate.
4 FrictionA force that opposes the motion of objects that touch each otherFriction happens at the surface of objects (where they touch)4 main types of friction
5 Static Friction Acts on objects that are not moving Always acts in the direction that is opposite of an applied forceKeeps an object from being moved across a surfaceStops acting on an object once the object is moving
6 Sliding Friction Acts on an object once the object is moving Goes against the direction in which the object is moving as it slides on a surfaceOccurs when two objects rub togetherLess of a force than static friction
7 Rolling Friction Force that acts on rolling (round) objects Acts on the surface and at the point where the object is touching something else (the ground for example)Allows the object to touch the ground and not slipSlows rolling objects down
8 Fluid FrictionForce that opposes an object’s motion through a fluid (liquid or gas)Force increases as the object’s speed through the fluid increasesWhen fluid friction acts on objects moving through the air, it is called air resistance.
9 Gravity Downward force that acts between any two masses An attractive force ~ pulls objects togetherActs over large distances (unlike friction)
10 Falling objects Forces acting on a falling object: Gravity (pulling downward)Air resistance (acts in opposition to gravity, reduces acceleration)Terminal velocity is reached when the force of air resistance equals the gravitational force.The object is no longer accelerating.V= a x t speed of a falling object
11 Projectile MotionThe motion of a falling object (called the projectile) after it has been given a forward velocity (example: throwing something forward)Air resistance and gravity act on the object.Because of the forward velocity and the downward gravitational force, the object will follow a curved path.