Physics: Understanding Forces

• Science is the study of the natural world based on facts learned through experiments and observation
• Physics is a branch of science that deals with matter, energy, motion, and forces

Forces

• A force is a push or pull that can change the motion of an object
• Forces are measured in newtons (N)

Types of Forces

• Gravitational force: The force of attraction between objects with mass
• Electromagnetic force: The force associated with electric charge and magnetism
• Strong nuclear force: The force that holds the nucleus of an atom together
• Weak nuclear force: The force responsible for radioactive decay

Contact Forces

• Contact forces require physical contact between objects
• Examples include:
  • Applied force: A force applied by a person or object
  • Frictional force: A force that opposes motion when two surfaces rub together
  • Tension force: The force transmitted through a rope, string, or cable when pulled tight
  • Normal force: The support force exerted on an object that is in contact with another object
  • Air resistance force: The force of air pushing against a moving object

Non-Contact Forces

• Non-contact forces act at a distance without physical contact
• Examples include:
  • Gravitational force: The force of attraction between objects with mass
  • Magnetic force: The force of attraction or repulsion between magnets or magnetic materials
  • Electrostatic force: The force of attraction or repulsion between electric charges

Effects of Forces

• Forces can cause objects to:
  • Start moving
  • Stop moving
  • Change direction
  • Speed up
  • Slow down
  • Change shape

Balanced Forces

• Balanced forces are equal in size and opposite in direction
• When forces are balanced, there is no change in motion
• The object remains at rest or continues moving at a constant velocity

Unbalanced Forces

• Unbalanced forces are not equal in size or opposite in direction
• When forces are unbalanced, there is a change in motion
• The object accelerates in the direction of the net force

Net Force

• Net force is the vector sum of all forces acting on an object
• If the net force is zero, the forces are balanced
• If the net force is not zero, the forces are unbalanced

Energy

• Energy is the ability to do work
• Energy is measured in joules (J)

Types of Energy

• Kinetic energy: The energy of motion
• Potential energy: Stored energy
  • Gravitational potential energy: Energy stored due to an object's height above the ground
  • Elastic potential energy: Energy stored in a stretched or compressed object, such as a spring
• Thermal energy: The energy of heat
• Chemical energy: Energy stored in chemical bonds
• Nuclear energy: Energy stored in the nucleus of an atom
• Electrical energy: Energy associated with electric charge
• Radiant energy: Energy of electromagnetic radiation (light)
• Sound energy: Energy of sound waves

Forms of energy

• Energy can exist in many forms such as heat, light, kinetic energy, potential energy, electrical, or chemical

Kinetic Energy

• Kinetic energy depends on mass and velocity
• Kinetic energy is given by the formula: KE = 1/2 * m * v^2, where KE is kinetic energy, m is mass, and v is velocity

Potential Energy

• Potential energy is stored energy
• An example of potential energy is a ball held in the air

Gravitational Potential Energy

• Gravitational potential energy depends on mass, gravity, and height
• Gravitational potential energy is given by the formula: GPE = m * g * h, where GPE is gravitational potential energy, m is mass, g is the acceleration due to gravity, and h is height

Energy Transformation

• Energy can be transformed from one form to another
• Examples of energy transformation:
  • A light bulb transforms electrical energy into light and thermal energy
  • A car engine transforms chemical energy into kinetic energy and thermal energy
  • A solar panel transforms radiant energy into electrical energy

Conservation of Energy

• Energy cannot be created or destroyed, but it can be transformed from one form to another
• The total amount of energy in a closed system remains constant
• This principle is known as the law of conservation of energy

Work

• Work is done when a force causes displacement
• Work is measured in joules (J)
• Work is given by the formula: W = F * d * cos(θ), where W is work, F is force, d is displacement, and θ is the angle between the force and displacement vectors

Relationship Between Work and Energy

• Work is the transfer of energy from one object to another
• When work is done on an object, its energy changes
• Positive work increases an object's energy
• Negative work decreases an object's energy

Power

• Power is the rate at which work is done
• Power is measured in watts (W)
• Power is given by the formula: P = W / t, where P is power, W is work, and t is time
• Power can also be expressed as: P = F * v, where P is power, F is force, and v is velocity