Forces: Friction and Gravity Notes and Questions

Force and Motion

We are going to continue our lesson on Force and Motion.

You will be taking notes and using them to answer the questions in this lesson. When completed, you will take a screenshot of your score and the notes to upload for a grade.

60 points total. 30 for notes/30 for Quizizz!

Describing Force and Motion

• How do we decide if something is moving? For example, if you are in the car with your friends...are your friends moving?

• Sure, their hands are going up and down, they are blinking, and most of us would say they are moving.

• What determines if something is moving or not?

Motion

• If an object is in motion, then its position changes when compared to another object.

• If you use yourself as a reference point for motion, then you might say that your friends are not moving. Or if you use the seat in the car as the reference point, again, you might say they are not moving.

• What if you used the stop sign on the corner of the road as the reference point? Are they moving now?

Motion

Because motion is determined by a reference point, and that reference point can change...we say that motion is relative.

So, if you are in a car and you use the trees on the side of the road as your reference point, then you are moving.

What happens if you change the reference point to your seat in the car? Are you still moving?

Multiple Select

Choose the correct answer: While I am sitting in my seat at school I am not moving relative to the

• Floor

• Sun

What is a force?

• When you move your chair, type on your keyboard, or sit at your desk you are applying a force.

• A force is a push or pull.

Multiple Choice

Does a force have to make physical contact with something? (can you think of one that doesn't?)

• yes

• no

Describing force

• A force is described by using an arrow pointing in the direction of the force. The longer the arrow, the stronger the force.

• The SI unit for force is a newton, named after Sir Isaac Newton.

Contact and Noncontact forces

• If you push a box across the floor, you are applying a contact force. The friction that works against you is also a contact force.

• The gravity holding you to the Earth is a noncontact force. Magnetism and electric forces are other examples of noncontact forces.

Multiple Select

Which of the following are a contact force?

• Hitting a baseball

• a magnet moving a train

• you opening the car door

• Friction between a bike tire and the sidewalk

Friction

What is Friction?

What factors affect friction?

Multiple Choice

Friction is a force that acts in an ___________ direction of movement.

• similar

• opposite

• parallel

• west

Multiple Select

Friction depends on what 2 factors?

• gravity

• type of surface

• force applied

• amount of time

Multiple Choice

What are the bumps on surfaces of objects that cause friction?

• microwelds

• welding

• microchips

• frictions

Multiple Choice

_____________ friction acts on objects that are not moving.

• sliding

• rolling

• static

• fluid

Multiple Choice

This photo represents...

• Air resistance

• water resistance

• friction force between 2 solid bodies

Multiple Choice

Which type of friction is shown in the picture?

• rolling

• static

• fluid

• sliding

Multiple Choice

Which type of friction is shown in the picture?

• fluid

• static

• rolling

• sliding

Multiple Choice

Sally experiences-

• Rolling Friction

• Sliding Friction

• Fluid Friction

• Static Friction

Vocabulary

Vocabulary

Here are some vocab terms you have or will see on the Gizmo activity- Gravity Pitch

Gravity

The force of attraction between all objects in the universe

Gravity

Gravity is only significant when one of the objects is very large, like the Earth. There is very, very little gravitational attraction between you and your couch – but there is some! 

BrainPOP Video

https://www.brainpop.com/science/natureoftheuniverse/gravity/

Poll

What makes an object have a stronger gravitational pull?

• it's size: if the object is large

• it's distance from another object

• it's mass: if it's heavier

Gravity increases as mass & size increases

Multiple Choice

As the mass of the objects DECREASES, gravity will...

• increase

• decrease

• stay the same

Multiple Choice

If the distance between object DECREASES and gets closer together, the force of gravity...

• increase

• decrease

• stay the same

Multiple Choice

REVIEW!

What is weight?

• Gravity acting on something with mass

• How heavy something is

• The thing you do in line at Disneyland

Gravity and Gravitational Attraction

• Gravity: Force that attracts all objects toward each other.

• Force of gravity (between two objects) is affected by the masses of the objects and the distance between them.

Multiple Select

What would increase the force of gravity between two objects?

• Increase in mass

• Decrease in distance

• Decrease in mass

• Increase in distance

Fill in the Blank

The force of gravity would __________ if the distance between the moon and earth decreased.

Inertia

• Inertia: The tendency of an object to resist a change in motion.

• An object with more mass has more inertia.

• Objects with more inertia are harder to move and stop.

• Newton's First Law: An object at rest will stay at rest, an object in motion will stay in motion unless acted on by a force.

Multiple Choice

Why does a baseball continue to move after a pitcher lets go of it and stops applying force?

• The ball has speed.

• The ball has inertia.

• The ball has gravity.

• The ball has friction.

Fill in the Blank

__________ will cause the ball to hit the ground.

Force and Motion Notes

You are still taking notes...

Forces

A force is a push or a pull on an object.

Force can be calculated with a formula:

force = mass x acceleration

(F=m x a)

Force is measured in units called Newtons (N).

Unbalanced Forces

Unbalanced Forces-When two forces acting on an object are not equal in size, we say that they are unbalanced forces.  Motion changes when we have unbalanced forces

Balanced Forces

When an object is at rest on a surface, such as the ground, its weight is balanced by the reaction force from the ground. The ground pushes up against the object. There is no acceleration with balanced forces.

Multiple Choice

What happens when two forces act in the same direction?

• the forces add together

• the forces cancel each other out

• the stronger force takes over

Other Forces

Did you know that gravity is a force? When the only force acting on an object is gravity, the object is in a state called "free fall"

Another force to note is air resistance. Air resistance is a force that opposes the motion of objects that move through the air.

Multiple Choice

Air resistance is considered to be a type of:

• motion

• speed

• friction

• weight

Mass and Inertia

Newton's 2nd law states that The greater the mass of an object, the more force it will take to accelerate the object. 

This also ties in to inertia, an object's tendency to resist a change in motion. The greater the mass an object has, the greater inertia it will have.

Multiple Choice

The greater the mass an object has, the greater the inertia.

• True

• False

Friction

Friction is a force opposing the motion between two surfaces. For example: Tires on roadway.

Types of Friction

Sliding Friction is friction that occurs when one solid surface slides over another.

Static Friction is friction that acts on objects that are not moving.

Fluid Friction is friction on a solid object as it moves through a liquid or a gas.

Rolling Friction is when a wheel, ball, or cylinder rolls freely over a surface, as in ball and roller bearings

Multiple Choice

Which type of friction is pictured?

• rolling

• sliding

• fluid

Multiple Choice

Which of the following would cause an increase in friction on our Hot Wheels ramp?

• add cooking oil to the ramp

• add sandpaper to the ramp

Newton's Laws of Motion

1st Law: An object at rest will remain at rest, and an object in motion will remain in motion unless acted on by an outside force.

2nd Law: An object accelerates because a force acts on it. The larger the force, the greater the acceleration. The larger the mass, the greater force needed to accelerate it.

3rd Law: For every action force, there is an equal and opposite reaction force.

Multiple Choice

Which of the following is an example of Newton's 1st Law of Motion?

• When you swim, you push the water backward and the water pushes you forward.

• A soccer player races to the motionless soccer ball and kicks it to overcome inertia.

Multiple Choice

Which of the following is an example of Newton's 2nd Law of motion?

• A snowboarder turns sideways and digs the board into the snow. The snow stops the board.

• It takes more force to kick a soccer ball 5 meters than it does to kick a beach ball 5 meters.

Multiple Choice

Which of the following applies to Newton's 3rd Law of motion?

• Water shooting out of a water hose causes the hose to fly backwards.

• We wear seatbelts in the car in case the car stops suddenly.