Forces and MotionForces and Motion

Ch 2 Sect 3Ch 2 Sect 3

ForcesForces

Force-a force is a push or pull that one Force-a force is a push or pull that one body exerts on anotherbody exerts on another A force can cause the motion of an object to A force can cause the motion of an object to

change change Example-Swinging a racketExample-Swinging a racket

Force is measured in the SI unit called Force is measured in the SI unit called newtonsnewtons

Types of ForcesTypes of Forces

There are 3 types of forcesThere are 3 types of forces1. Balanced Force-Forces on an object are 1. Balanced Force-Forces on an object are

equal and opposite in directionequal and opposite in direction

10 Newtons 10 Newtons

Types of Forces (cont)Types of Forces (cont)

2.2. Unbalanced force-Forces are pushing Unbalanced force-Forces are pushing against each other with unequal forceagainst each other with unequal force

Unequal forces lead to motion of an objectUnequal forces lead to motion of an object

10 Newtons 5 Newtons

Motion

Types of Forces (cont)Types of Forces (cont)

3. Net force- net forces are the sum or 3. Net force- net forces are the sum or

accumulation of all forces on the objectaccumulation of all forces on the object Add up all the forces on the object to find the Add up all the forces on the object to find the

net forcenet force Net force occurs in the direction of the larger Net force occurs in the direction of the larger

forceforce

InertiaInertia

Inertia is the tendency of an object to Inertia is the tendency of an object to resist change in its motionresist change in its motion Mass and weight are related to inertiaMass and weight are related to inertia

The greater the mass the greater the inertiaThe greater the mass the greater the inertia

Law of InertiaLaw of Inertia

Law of inertia is Newton's 1Law of inertia is Newton's 1stst law of law of motionmotion An object moving at a constant velocity An object moving at a constant velocity

keeps moving at that velocity until a force keeps moving at that velocity until a force acts upon it. An object at rest stays at rest acts upon it. An object at rest stays at rest until a net force acts upon ituntil a net force acts upon it

Law of Inertia SimplifiedLaw of Inertia Simplified

Something that is moving, will keep Something that is moving, will keep moving until it is stoppedmoving until it is stopped

Something that is sitting still will keep Something that is sitting still will keep sitting still until you push/pull/hit itsitting still until you push/pull/hit it

Questions Relating to Questions Relating to InertiaInertia

When you throw a ball up as hard as you When you throw a ball up as hard as you can why doesn’t it keep going?can why doesn’t it keep going?

How does a human not wearing a How does a human not wearing a seatbelt demonstrate the law of inertia in seatbelt demonstrate the law of inertia in a car crash?a car crash?