5. forces

• distance is how far an object moves
• distance does not involve speed
• distance is a scalar quantity
• displacement involves 2 things
• displacement involves the distance an object moves from start to finish - measured in a straight line - and direction of straight line
• displacement is a vector quantity
• contact forces examples active forces, resistive forces, tension, compression, reaction, turning force, upthrust
• active force - push/pull
• resistive forces - eg air resistance,drag,friction always act against motion
• tension force - stretching
• compression force - squasghing
• reaction force - opposes action forces
• turning force - twist, torque
• upthrust force - upward force from a fkuid
• non-contact forces examples - grravitational, magnetic , electrical
• gravitational force - attractive forces between objects with mass , bigger the mass the stringer the force
• magnetic force - attractive / repulsive force between magnetic materials
• electrical force - attractive / repulsive force betweeen charged materials
• a scalar only has a magnitude or size
• a vector has a size and direction
• a resultant force is a single force that has the same effect as the other forces on an object combined
• resultant forces can change the motion of objects - speed up, slow down
• resultant forces can change shape of objects - stretch or squash
• gravity is a non-contact force attractive force between masses
• weight = mass x gravitational field strength
• W = mg
• work is done when a force moves through a distance
• work done = force x distance in force direction
• elastic materials. - return to its original shape when force removed
• plastic materials - keeps it's new shape and does not return to it's original shape when force removed.
• extension = new length - original length
• spring constant (K) - the force needed for a metre extension - also called spring stiffness
• force (N) = spring constant (n/m) x extension (m)
• F= ke
• work done (J) = 1/2 x spring constant (n/m) x extension squared (m)
• K = spring constant
• pressure - force per unit area
• pressure is calculated using the formula - pressure = force/area
• pressure is measured in Newtons per square metre or pascals (pa)
• density - mass per unit volume