FORCES AND MOTION REVIEW

DEFINE FORCE A push or pull on an object

WHAT IS A NET FORCE? Total amount of force applied to an

object

WHAT IS THE WEIGHT OF A 20 KG DOG?W=20kg * 9.8m/s²W= 196N

WHAT IS THE UNIT OF MEASURE FOR WEIGHT AND FORCE? Newton

A PORSCHE 911 ACCELERATES FROM REST TO 4.7M/S². THE MASS OF THE CAR IS 1400 KG. WHAT IS THE AVERAGE NET FORCE THAT ACTS ON THE PORSCHE?

F=MAF= 1400 * 4.7F= 6,580 N

NAME THE 4 TYPES OF FRICTION Static Rolling Sliding Fluid

WHY DON’T OBJECTS STAY MOVING HORIZONTALLY FOREVER? Gravity and air resistance

WHAT TYPE OF FRICTION IS AIR RESISTANCE? Fluid friction

DESCRIBE WHAT HAPPENS WHEN AN OBJECT REACHES TERMINAL VELOCITY

The object is no longer accelerating; force of gravity is equal to the force of air resistance

A BULLDOZER PUSHES A 60KG CRATE WITH A FORCE OF 180 N. THE FORCE OF FRICTION ON THE CRATE IS 60 N IN THE OPPOSITE DIRECTION. WHAT IS THE ACCELERATION OF THE BOX?

120N=60kg* a120/60=a20m/s²=a

DEFINE PROJECTILE An object in which the only force acting

is gravity

AN EMPTY AIRPLANE HAS A MASS OF 30,400 KG AND A TAKEOFF ACCELERATION OF 1.20M/S².WHAT IS THE NET FORCE ACCELERATING THE PLANE? F=MA F=30,400 * 1.2m/s² F=36,480 N

WHAT IS ANOTHER NAME FOR NEWTON’S FIRST LAW? Law of Inertia

DEFINE INERTIA Resistance of an object to change its

motion

USING A VECTOR ARROW, WHAT DOES THE LENGTH OF THE ARROW REPRESENT?

The magnitude (strength)

HOW CAN YOU TELL WHICH DIRECTION THE NET FORCE IS BEING APPLIED?

The head of the arrow points in the direction of the force

HOW DOES A BALANCED FORCE AFFECT THE MOTION OF AN OBJECT?

Motion is unchanged if the force is balanced

DEFINE SPEED The distance traveled over a certain

amount time

HOW ARE SPEED AND VELOCITY DIFFERENT? Speed is a scalar quantity (magntude

only) and velocity is magnitude and direction

WHAT HAPPENS TO AN OBJECT’S ACCELERATION WHEN A FORCE IS INCREASED? The acceleration increases

HOW ARE MASS AND INERTIA RELATED? The greater the mass the greater the

inertia

TWO TUGBOATS ARE MOVING A BARGE. TUGBOAT A EXERTS A FORCE OF 3000 N TO THE RIGHT. TUGBOAT B EXERTS A FORCE OF 5000 N IN THE SAME DIRECTION. WHAT IS THE NET FORCE ON THE BARGE? ( USE ARROWS TO ILLUSTRATE INDIVIDUAL AND NET FORCE ON THE BARGE)

HOW DOES SURFACE ROUGHNESS AFFECT FRICTION? The rougher the surface the greater the

friction

A CAR IS TRAVELING AT 50MPH. HOW LONG WILL IT TAKE THE CAR TO TRAVEL 300 MILES?

300/50T=6 hrs

IF YOU DOUBLE THE FORCE EXERTED ON AN OBJECT HOW DO YOU KEEP THE ACCELERATION THE SAME?

Increase the mass

HOW ARE ACTION AND REACTION FORCES RELATED ACCORDING TO NEWTON’S THIRD LAW?

Reaction forces are of equal force to the action but in opposite direction

HOW DOES AN UNBALANCED FORCE AFFECT AN OBJECT’S MOTION?

It changes the speed or direction

WHAT IS THE WEIGHT OF A ROCAK THAT HAS A MASS OF 7KG?

F=M*AF= 7 * 9.8F=68.6 N