8.2.2-Newton's First Law

​Identifying Forces

Identifying forces allows us to figure out what different forces are in play and what each force is doing when we observe a specific action.​

​

​The image to the right shows "pull" forces. If the force of the guy on the right is greater than the force against him from the guy on the left, then he will pull the other guy towards him.

​Identifying Forces

The combination of all the forces acting on an object is the net force. In the image to the right, the net force is greater with each person moving in the same direction.

​

​In the bottom image, the two forces push against each other and are subtracted from each other. The guy with the greater force pushes the block towards the other guy.

Net Force

If multiple forces move in the same direction, their strengths are added together. If multiple forces move in opposite directions, their forces are subtracted and the greater force moves the object in its direction.​

​Balanced and Unbalanced Forces

​If forces moving in opposite directions are equal, then the forces are balanced and there is no movement of the object.

​

​If forces moving in opposite directions are not equal, then the forces are unbalanced and the object moves.

​Balanced and Unbalanced Forces

​So, balanced forces are forces acting on an object that combine and form a net force of zero.

​

Unbalanced forces are forces acting on an object that combine and form a net force that is not zero.

Multiple Choice

True or False:

Balanced forces cause an object to change its motion.

• True

• False

​Newton's First Law of Motion

​Newton's First Law of Motion states, if the net force on an object is zero, then the motion of the object does not change.

​

​This means an object at rest stays at rest if it isn't acted on by an outside force. And an object in motion stays in motion unless acted on by an outside force.

​Inertia

​The tendency of an object to resist a change in its motion is called inertia. This is observable in

​the jerking feeling you get

​when a car stops quickly

​because the car stops, but

​your body tries to keep going.

Multiple Choice

_________________ is an object's tendency to resist a change in motion.

• inertia

• malleability

• net force

• balanced forces

Multiple Choice

If two people push a dresser in the same direction, one at 50 newtons and the other with a force of 100 newtons, how much net force is acting on the dresser?

• 150 N

• 50 N

• 200 N

• 100 N

Multiple Choice

______________________ is any push or pull on an object.

• Force
• Mass
• Gravity
• Air Resistance

Multiple Choice

A _________ uses force to move an object towards you. 

• Pull
• Push
• Motion
• Force

Multiple Choice

A ________ uses force to move an object away from you. 

• Push
• Pull
• Gravity
• Motion

Multiple Choice

If I kick a soccer ball across the field, what vocabulary word tells me why the ball would slow down in the grass?

• acceleration
• friction
• gravity

Multiple Choice

The force that pulls all objects toward each other is called_______?

• push
• pull
• gravity
• mass

Multiple Choice

The change in position of an object.

• Acceleration
• Motion
• Equilibrium
• Unbalanced Force

Multiple Choice

A force that resists the movement of one surface past another surface.

• Acceleration
• Gravity
• Friction
• Lubricant

Multiple Choice

If you pull the cord, what direction will the box move?

• Up
• Down
• Left
• Right

Multiple Choice

Basic SI unit of length or distance is:

• Meter

• Seconds

• Grams

• Minutes

Multiple Choice

Which of the following choices is an example of VELOCITY?

• 35 mph

• 35 meters

• 35 mph EAST

• 35 minutes

Multiple Choice

Which of the following is an example of a SPEED?

• 35 seconds

• 45 minutes

• 60 mph (miles per hour)

• 50 meters

Multiple Choice

Speed in any given direction is:

• Acceleration

• Average speed

• Velocity

• Slope

Multiple Choice

The rate at which velocity changes and can be seen by speeding up, slowing down, or changing direction:

• Speed

• Velocity

• Acceleration

• Slope

Multiple Choice

If an object in motion is not acted on by an unbalanced force, it will continue with the same speed and direction.

• True

• False

Multiple Choice

An object's tendency to resist change in its state of motion.

• gravity

• force

• inertia

• friction

Multiple Choice

An object at rest will stay at rest unless an unbalanced force acts on it.

• True

• False

Poll

Rate your understanding of motion and Newton's First Law.

• Level 0- Even with help, I still don't understand.

• Level 1- I'm starting to get it, but I'm still confused.

• Level 2- I can do this help, or with an example in front of me.

• Level 3- I can do this on my own. I can show I understand.

• Level 4- I am very confident with this. I can teach someone how to do this.

Multiple Choice

Newton's 1st Law is also called the Law of ...

• Friction

• Inertia

• Unbalanced forces

• Newtons

Multiple Choice

An object in motion tends to stay in motion unless an ___ force acts on it.

• unbalanced
• balanced

Multiple Choice

The tendency of an object to resist a change in motion is...

• inertia
• kinetic energy
• vector
• net force

Multiple Choice

Objects with greater _________ also have greater inertia.

• speed
• mass
• temperature
• friction

Multiple Choice

The law of inertia (Newton’s First Law) applies

• to both moving and nonmoving objects
• only to moving objects
• only to objects that are not moving

Multiple Choice

Because of inertia, a moving object will keep ________ unless acted on by an unbalanced force.

• at rest

• moving

• in one spot

• inertia

Multiple Choice

Because of inertia, a resting object will remain at ________.

• rest
• a constant speed
• school
• inertia 

Multiple Choice

What kind(s) of objects have inertia?

• all objects with mass
• only objects at rest
• only objects in motion
• only objects whose motion is being changed

Multiple Choice

You push on a car and it does not move.  What is true about the inertia?

• The inertia is changing
• The inertia of the car is too great 
• The inertia of the person is equal to the car
• There is not inertia because of no movement

Multiple Choice

Galileo found that a ball rolling down one inclined plane would roll how far up another inclined plane? 

• The ball would not rull up the other plane at all. 
• to nearly the original height
• to nearly twice the original height. 
• to nearly half it original height

Multiple Choice

An object following a straight-line path at a constant speed 

• has zero acceleration
• has no forces acting on it
• has a net force acting in the direction of motion
• none of these

Multiple Choice

One object has twice as much mass as another object. The first object also has also twice as much...

• velocity
• gracitational acceleration
• inertia
• all of these

Multiple Choice

If a hockey puck slides on a frictionless force it will eventually slow down because of its inertia.

• True
• False

Multiple Choice

Objects at rest remain at rest and objects traveling at a steady rate in a straight line continue that way until a _________acts on them.  

• force
• velocity
• inertia
• acceleration 

Multiple Choice

Why is the net force 0 in the image?

• Because the elephants are the same size
• Because they are both pulling the same amount of force in opposite directions
• Because they are elephants
• Because they are pulling away from each other.