Newton's 1st Law and Balanced/Unbalanced Forces

Newton's 1st Law and Balanced/Unbalanced Forces

Newton's First Law

AKA the law of INERTIA

"An object in motion will stay in motion (at a constant velocity in a straight line) and and object at rest will stay at rest unless acted on by an UNBALANCED force."

What is inertia?

Intertia is latin for "lazy"

Everything with mass has inertia. The more mass, the more inertia.

Objects want to keep doing whatever they were doing - they resist a change in motion.

Mass and Inertia

Heavier objects have more inertia. It is harder to change their motion.

Multiple Choice

What is inertia?

• the force that opposes motion
• the force of attraction between 2 objects
• an object's tendency to stay in motion or to stay at rest
• a change in an object's speed and/or direction

Multiple Choice

True of False?
An object's inertia is effected by its mass.

• False
• True

Multiple Choice

Which has more Inertia? 

• Truck
• Ant
• A cat
• A skateboard

Multiple Choice

Why does an 18-wheeler have more inertia than a bicycle?

• it has more mass
• it has more volume
• it is not as aerodynamic

Multiple Choice

Which type of force(s) will cause a change in an object's motion?

• gravity
• zero net force
• balanced forces
• unbalanced forces

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

What is a force?

Forces are pushes or pulls acting on objects.

Forces are measured in Newtons (N).

Balanced Forces

If the forces acting on an object are balanced, it means the NET FORCE is zero.

The force in one direction is "cancelled out" by a force in the opposite direction.

The object will either remain at REST or CONSTANT VELOCITY.

Unbalanced Forces

If the forces acting on an object are unbalanced, it means there is a NET FORCE.

There is more force in one direction than another.

The object will ACCELERATE in the direction of the net force.

Finding Net Force

We subtract forces in opposite directions from each other - just like we've done with other vectors we've looked at!

Multiple Choice

Look at the diagram. What would be the direction of the motion ?

• movement to the left
• movement to the right
• no movement

Multiple Choice

Calculate the net force shown in the  diagram?

• 6 N
• 0 N
• 3 N
• 9N

Multiple Choice

8 N to the left , and 4 N to the right. Find the net force. Is this balanced

• 12 N Right No

• 12 N Right Yes

• 4 N Left Yes

• 4 N Left No

Multiple Choice

Find the net force: 15 N to the right, and another 15 newtons to the right.

• 0 N Right
• 0 N Left
• 30 N Left
• 30 N Right

Multiple Choice

Calculate the net force shown in the  diagram?

• 41 N
• 25 N
• 16 N
• 9 N

Multiple Choice

Calculate the net force shown in the  diagram?

• 0N
• 400 N
• 600 N
• 800 N

Multiple Choice

What is the net force of this object?

• 0N
• 50N
• 25N
• 5N

Multiple Choice

An object is moving but has BALANCED forces acting on it. What will happen to its speed?

• moving at a constant speed

• stop moving

• slow down

Multiple Choice

If a car has a force of 54 N forwards and the brakes have a force of 73 N backwards, what is the overall Net Force.

• 16 backwards

• 19 forwards

• 18 backwords

• 23 forwards

Multiple Choice

What is the net force?

• 17 N Right
• 3 N Right
• 3 N Left
• 17 N Left

Multiple Choice

What is a force?

• the PUSH or PULL on an object 
• The MOTION an object creates
• The objects HITTING one another
• Going REALLY FAST

Multiple Choice

Which one is balanced?

• top

• bottom

• both

Multiple Choice

Forces that are acting in opposite directions should be subtracted from each other.

• True

• False