forces

• Friction is a force that slows down a moving object due to two surfaces rubbing on each other
• The greater the friction, the faster an object will slow down or the greater the force needed to overcome the friction
• Drag is the force that slows down an object moving through a fluid (liquid or gas) by colliding with fluid particles
• Both drag and friction are contact forces as surfaces in friction and object and fluid particles in drag come into contact with each other
• Both drag and friction are measured in Newtons (N)
• A moment is the turning effect of a force, measured in Newton meters (Nm)
• The size of a moment increases as the distance from the pivot or the force size increases
• Equilibrium is when an object like a seesaw is balanced, with equal and opposite clockwise and anticlockwise moments
• Extension is the amount a spring stretches when a force is applied, reaching its elastic limit
• Hooke's law states a linear relationship between force applied to a spring and its extension
• Gas pressure is caused by gas particles colliding with the container walls, with higher pressure from more frequent collisions
• Atmospheric pressure is the pressure exerted by air, decreasing at higher altitudes due to fewer particles weighing down
• Pressure on a solid is known as stress, with lower pressure over a larger area, seen in snowshoes
• Liquids are incompressible, transferring pressure and increasing with depth due to the weight of water above
• The pressure in liquids depends on the weight of the water above, increasing with more water molecules above
• Pressure can be calculated as force divided by area