Force and Motion Review

Force and Motion Review

Read through the slides and answer the questions as you go.

Motion, Speed, Velocity, and Inertia Review

Motion is a change in position.

Speed is the distance an object travels in a certain amount of time.

Velocity is the speed and direction of a moving object.

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

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.