Chapter 4

Newton’s 2nd Law~ Newton’s 2nd law of motion says that a net

force acting on an object causes the object to

accelerate in the direction of the force.

~The acceleration is determined by the size of the force and the mass

of the object. 

~A larger mass requires a greater force than a smaller mass would

require to achieve the same acceleration.

The Force Equation!•       Newton’s 2nd Law can be

expressed in a equation form like this:

  Force = mass x acceleration

F= ma

Mass is expressed in kilograms and acceleration is expressed in

m/s2. A Newton is the amount of force

needed to accelerate an object with a mass of 1kg at an

acceleration of 1m/s2. In other words, 1 N = 1 kg x m/s2.

When you have a larger mass like the bowling ball or you toss a hippo and a cat in the air the

hippo will land first because of the inertia, because when you have a larger mass the more inertia you will have. It is opposite like if you have a

smaller object the less inertia you will have.

Acceleration Caused by Gravity!

At the Earth’s surface, gravity causes all falling objects to accelerate at 9.8 m/s2.

Because any force can be calculated by using this equation:

F =m x a.The weight of an object(W) is the force of

gravity acting on its mass. W = m x a.

So the last equation we could do would be W = m x 9.8m/s2

Acceleration due to gravity is the same for all objects, regardless of the mass. Air resistance is the force air exerts on

a moving object.This force acts in the opposite

direction to that of the objects motion.In case of a falling object, air

resistance pushes up as gravity pulls down.

Terminal Velocity is the highest velocity that will be reached by a

falling object.Air Resistance gradually

increases until it balances the pull of gravity.

Projectiles and Circular MotionProjectiles!

A projectile is anything that’s been thrown or shot through the air.

~Horizontal Motion~Horizontal motion that is,

motion parallel to the Earth’s surface.

Vertical Motion!•       Vertical motion is when gravity starts pulling it downward, or motion

perpendicular to Earth’s surface. Gravity exerts an unbalanced force

to the ball.Gravity exerts an unbalanced force to the ball,changing the direction of

it’s path from forward only to

forward and downward.

Motion Along Curves•     Centripetal Acceleration is when acceleration toward the center of a curved or circular

path.  

The word centripetal means”

toward the center”

~Centripetal Force~•       This is when the force is acting

toward the center of a curved or circular path.

•       When a car rounds a sharp

curve on a highway, the centripetal force is the friction between the tires

and the road surface.

*Weightless in Orbit*•       To be truly weightless, the

astronauts would have to be free from the effects of gravity.

•       Orbiting 400 km above Earth, the shuttle and everything inside it

still respond to those effects.•       In fact, the gravity keeps the shuttle in orbit just like when the astronauts do when they leave the

shuttle in space.

•      The object would seem to be weightless.•      When an object is influenced only by

gravity, it is said to be in free-fall.•      An orbiting space shuttle and all it’s

contents are in free-fall around Earth.When you are up there in space you would

see like in movies that when you are floating in the air so are the other objects around you.