Inertia: Resistance to the push / pull (force)

newton's first law of motion

Learning Target

AP#1

I can define the combination of all forces acting upon an object as net force.

Explain the law of inertia and give a real world example.

Starter

Tug-O-War:

Video summary

Balanced Forces

Un-Balanced Forces

Unbalanced Forces

Causes Acceleration

10N

Subtracting Forces

5 N

Object

10N

Write two to three sentences about the video. Explain what is exactly occurring in each segment.

10N

Subtracting Forces

10N

5 N

Balanced and unbalanced force practice

Notice that all the forces are unequal and pointed in the opposite direction. Hence they are unbalanced and in opposition to each other – or one partially cancels the other.

= 5 N

Complete the worksheet provided for discussion. You have 10 mins to complete.

AP#2

5 N

Explain the motion of balanced and unbalanced forces.

10 N

Summarization

Unbalanced Forces

Causes Acceleration

Two forces can subtract to produce a net force in the direction of the larger force.

Negative Acceleration occurs (Slow Down)

The picture below helps us to explain newton's first law. Explain the importance of how it helps us.

Adding Forces

Object

5 N

Notice that all the forces are pointed in the same direction. Hence they add together.

5 N

Balanced Forces

(Balanced Forces = No Acceleration)

Adding Forces

= 10 N

Wait a minute. This object was moving.

That’s Right. As you may have noticed, although I may have balanced forces, I might still be moving.

Notice that when the forces are balanced, the object might still be moving, but the objects are not accelerating, instead they have a constant velocity. Hence, once in motion – it’s always in motion unless acted upon by what? Another Force.

5 N

Daily reflection

Notice that all the forces are equally pointed in the opposite direction. Hence they balance each other – or cancel each other.

5 N

Must have a check by me to be counted other than that it is a zero (0).

Object

Two forces can add together to produce a larger net force than either original force.

Positive Acceleration occurs (Speed up)

Forces may cancel each other and produce No Acceleration!

5 N

Equal Pushing

Equal Pulling

Subtracting Forces

Unbalanced Forces

Causes Acceleration

Distance [m]

Constant Velocity

0 1 2 3 4 5 6

5 N

Adding Forces

1

In other words, you still need to use the gas peddle to balance out all the force of friction to keep you going at a constant speed.

2

3

Time [Sec]

4

5

10 N

5 N

Equal Pushing

Equal Pulling

Balanced Forces

(Balanced Forces = No Acceleration)

Acceleration

5 N

To get an object to move faster, create an unbalanced force!

5 N

1

5 N

2

Forces may cancel each other and produce No Acceleration!

Balanced Forces

(Balanced Forces = No Acceleration)

Video: Bill Nye_Balance [1:51min]

Balanced v. Unbalanced

Ground pushes up

If these football players push

on each other equally as hard,

will either one move?

Gravity pulls down

Where would I place this to balance out the lever?

To keep the lever balanced - D x M = D x M

Gravity pulls down on you…

The ground pushes back up…

THIS KEEPS YOU WHERE YOU ARE!

Balanced Forces

(Balanced Forces = No Acceleration)

Balloon Lab

Newton's first law of motion

Velocity

Acceleration

Normal

5 N

Object

5 N

Equal Pushing

Notice that all the forces are equally pointed in the opposite direction. Hence they balance each other – or cancel each other.

Gravity

Forces may cancel each other and produce No Acceleration!

Balanced v. Unbalanced Forces

Balloon Lab

Velocity

Acceleration

Normal

If all forces are balanced there is no acceleration in any direction.

(Either Zero Motion or Constant Velocity)

If one force is greater than the opposing force we get acceleration in a direction.

Force (Friction)

Force (Thrust)

Gravity

Force

Balloon Lab

Velocity

What is force?

Push or Pull

It’s what causes “things” to accelerate

Acceleration

Normal

Force (Friction)

1000 kg

Gravity

Newton’s Law of Motion says:

Inertia: Resistance to the push / pull (force)

Newton’s 1st Law of Motion:

once in motion an object stays in motion - unless acted upon by another unbalanced force.

An object at rest stays at rest – unless acted upon by another unbalanced force.

(7 Inertia Demos)

“In order to move an object with mass,

you need to apply a force”

The greater the mass = The greater inertia => more force is needed

Balanced & Unbalanced Forces

Second Law of Motion:

Forces Instant Replay

Acceleration depends on the object’s mass and the net force acting on the object.

To move a mass, you need to apply a force

More Force = more Acceleration

More Mass = less Acceleration

an object at rest tends to stay at rest, and an object in motion tends to stay in motion, with the same direction and speed.

Newton's first law of motion

“For every action there is an equal and opposite reaction.”

Rockets take off because of a force downwards from the bottom makes them accelerate in the opposite direction!

Ex: Skateboard Demo/ Wall

Upwards

motion

Downwards

force