Forces and Newton’s Laws

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# Forces and Newton’s Laws - PowerPoint PPT Presentation

Forces and Newton’s Laws. Tina R. Walters 2011. Forces. A push or a pull. What is a Net Force?. T he combination of all the forces on an object. Determines the motion of the object . Same Direction Add the forces together Opposite Directions The difference

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### Forces and Newton’s Laws

Tina R. Walters

2011

Forces

A push or a pull

What is a Net Force?
• The combination of all the forces on an object.
• Determines the motion of the object.
• Same Direction Add the forces

together

• Opposite Directions The difference

between the 2 forces and in the

directions of the larger force.

Forces

Balanced

• Cancel each other out
• No motion
• Net force equals zero

Unbalanced

• Net Force is more than zero
• Motion occurs
Newton’s First Law

When the net force acting on an object is zero, the object will remain at rest. If the object is already in motion. It will continue to move in a straight line.

Friction
• The force that acts to resist sliding between 2 touching surfaces.
• Always slows a moving object.
Three types of Friction
• Static prevents an object from moving when force is applied.
Three types of Friction
• Sliding slows down an object

that is sliding

Example: Brakes.

Three types of Friction
• Rolling Friction Occurs between the ground and part of the tire touching the ground. Pushes bike forward
Newton’s Second Law

An object acted on by a force will accelerate in the direction of the force.

Acceleration

Acceleration = net force (N)

(meters/second) mass (kg)

Acceleration

a = Fnet

m

Forces are measured in newton

N = kg-m/s2

Gravity
• Pulls objects towards each other
• Depends on the mass of an object and the distance between them.
Weight

Gravitational forces between you and the Earth.

Weight vs. Mass
• A force
• Measured in Newtons
• Varies with location.
• Amount of matter in a object
• Measured in Kg.
• Stays the same
Air Resistance
• Form of friction
• Gets larger as an object moves faster
• Depends on the shape of an object.
Center of Mass

Point in an object that moves as if all the object’s mass were concentrated at that point.

Newton’s Third Law

For every action there is an equal but opposite reaction.

Action-Reaction Pairs don’t cancel each other

Thrust

A force that lifts rockets

Free Fall

Only force acting on an object is gravity.

Weightlessness

Occurs in a free fall when the weight of an object seems to be zero.