Physics Part 2 forces

What is a force?

A push or a pull upon an object that can change its speed, direction, or shape.

What are the two main types of forces?

Contact and non-contact forces

What are contact forces and provide examples

Contact forces happen when two objects physically touch each other.

• Friction: Resistance that happens when two surfaces slide or try to slide against each other.

• Normal Force: The support force a surface gives an object, pushing perpendicular to that surface (like a table holding up a book).

• Tension: The pulling force carried through a stretched rope, string, or cable.

• Applied Force: A direct push or muscle pull exerted on an object by a person or another object.

• Air Resistance: A type of frictional drag that slows down objects moving through the air.

• Spring Force: The push or pull exerted by a stretched or compressed spring.

What are non-contact forces and provide examples

Non-contact forces act over a distance without any direct physical touch.

• Gravitational Force: An invisible pull of attraction between any two masses in the universe (such as Earth keeping you on the ground).

• Magnetic Force: The pull or push between magnetic materials and magnets.

• Electrostatic (Electrical) Force: The push or pull interaction between electrically charged particles

Mass vs weight

Feature	Mass	Weight
What is it?	Amount of matter in an object	Force of gravity pulling on an object
Does it change?	No, it is constant everywhere	Yes, it changes based on location
Measurement Unit	Kilograms (kg) or grams (g)	Newtons (N) or pounds (lbs)
Example (You on the Moon)	Your mass is exactly the same	You weigh about 1/6th of what you do on Earth

What are balanced forces?

A balanced force occurs when two or more forces acting on an object are equal in magnitude (strength) and opposite in direction, resulting in a net force of zero.

A Book on a Table: The downward pull of gravity on the book is equal to the upward support (normal) force exerted by the table.

• Tug-of-War (Stalemate): Two teams pulling on a rope with the exact same amount of strength in opposite directions, causing the rope to stay in one place.

• A Hanging Lamp: The downward weight of the lamp is balanced by the upward tension of the chain holding it

What are unbalanced forces?

a push or a pull that is not opposed by an equal and opposite force, resulting in a net force greater than zero that changes an object's motion.

Tug-of-war: When one team pulls harder than the other team, the rope moves toward the stronger team.

• Rocket launch: The upward thrust from the rocket engine is stronger than the downward pull of gravity.

• Kicking a ball: Your foot exerts an extra force on a stationary or moving soccer ball, changing its speed and path

What is a free body diagram?

A free body diagram is a simple drawing that shows an object by itself with arrows representing every external force acting on it

What is a scalar quantity?

A scalar quantity is a physical measurement that has only magnitude or size, with no associated direction.

What is a vector quantity?

A vector quantity is a physical measurement that has both a magnitude (size or value) and a specific direction.

Explanation of forces diagram

First force minus second is pos then its accelerating.
Two forces are equal that it is constant *any no other than 0
If the two forces are equally 0 then it is stationary
If the second force is higher than the first than it is deaccelerating

what quantity is force?

vector

Displacement and distance

Distance is the total length of the path an object travels, while displacement is the overall change in position from start to finish

Speed vs velocity

Speed, a scalar quantity, is a measure of how fast something is moving. It is calculated by dividing the distance travelled by the time taken. Your speed at any moment is called your instantaneous speed.

A car speedometer indicates the instantaneous speed of a car at that precise moment (Figure 3.1.5). Average speed is a measure of how fast something moves over a given time interval, such as over its whole journey. This ignores any stops or changes in speed that happen in any journey.

Velocity is not the same as speed—it is a vector quantity. It is calculated by dividing the displacement travelled by the time taken. The direction of the velocity vector is always the same as the direction of the displacement vector. For example, if a car has a displacement of 45 km north in 1 hour, then its average velocity is 45 km/h north

Acceleration

Acceleration is the rate at which an object changes its velocity over time.

What are newton’s laws of motion?

Isaac Newton published three laws of motion that explain how everything moves. Newton’s laws of motion are three physical laws. They describe the relationship between the motion of an object and the forces acting upon it; that is, how objects move or remain stationary in response to those forces.

What is newton’s first law of motion?

An object remains at rest or remains in motion at a constant speed and direction unless acted on by a net external force.

interia

Key terms

inertia the tendency of an object to resist change in its motion

Newton’s second law of motion

Interpreted two ways;
Heavier objects require a greater force to achieve the same acceleration as a lighter object.

Larger forces cause greater acceleration.

For example, to achieve a given acceleration, a person would need to push a car with a much greater force than they would need to push a child’s pram. The car has much greater inertia, so it is much harder to get it moving. Alternatively, if more people were to help push the car with greater force, the car would accelerate more.

Newton’s third law of motion

This law states that for every action, there is an equal and opposite reaction. This means that if a force is acting on an object, there is an equal force acting in the opposite direction to the applied force. These forces are called action–reaction force pairs.

There are always two objects experiencing these forces—in this case, the force on the girl is paired with the force on the dog. The action force and reaction force in an action–reaction pair always work on different objects. In the example, the force of the dog pulling the girl forwards can be considered the action and the force of the girl pulling backwards on the dog can be considered the reaction

magnitude

size o

mass

amount of matter in a substance or object