 # Forces.

## Presentation on theme: "Forces."— Presentation transcript:

Forces

What Is a Force? Force- a push or a pull that acts on an object
Can cause a resting object to move, or it can accelerate a moving object Forces are measured in Newtons (N) One newton is the forces that causes 1 kg mass to accelerate at a rate of 1 meter per second each second 1 N = 1 kg*m/s2

Representing Force Forces can’t be seen, but their effects can. So we have come up with a way to represent forces

Forces can be combined Forces in the same direction add together
Forces in opposite directions subtract from one another The net force is the overall force acting on an object after the forces are combined

Balanced and Unbalanced Forces
When forces on an object are balanced, the net force in zero and there is no change in the object’s motion When an unbalanced force acts on an object, the object accelerates

Friction A force that opposes the motion of objects that touch as they move past each other 4 main types of friction: 1.) static friction 2.) sliding friction 3.) Rolling friction 4.) fluid friction

Static Friction Acts on object that are not moving
Always acts in the direction opposite to that of the applied force You experience static friction every time you take a step

Sliding Friction Force that opposes the direction of motion of an object as it slides over a surface - Less than static friction. Therefore, less force is needed to keep an object moving than to start it moving

Rolling Friction Friction force that acts on rolling objects
100 to 1000 times less than the force of static or sliding friction Helps explain why professional movers use wheeled dollies to move heavy objects

Fluid Friction Opposes the motion of an object through a fluid
Examples can be seen on a submarine moving through water or an airplane flying through air You can feel fluid friction when stirring thick cake batter Increases as the speed of the object moving through the fluid increases Fluid friction acting on an object moving through the air is known as air resistance

Gravity Force that acts between any 2 masses
-attractive force—pulls objects together -does not require objects to be in contact -can act over long distances -Earth’s gravity acts downward toward the center of Earth

Falling Objects Gravity causes objects to accelerate downward, whereas air resistance acts in the direction opposite to the motion and reduces acceleration

Falling objects As objects fall to the ground, they accelerate and gain speed Terminal velocity is the constant velocity of a falling object when the force air resistance equals the force of gravity -the doesn’t mean the objects stop in mid air…it just means it doesn’t accelerate anymore Mass does NOT matter, all objects fall at the same rate

Projectile Motion The motion of a falling object (projectile) after it is given an initial forward velocity. Air resistance and gravity are the only forces acting on a projectile