Physics - P5 Notes

Forces and Work Done

• Vector quantities have a magnitude and a direction but scalar quantities only have magnitude and no direction
• Time is a scalar quantity
• Contact forces are ones that have to be touching by non-contact forces don't need to be touching
• Mass is the amount of 'stuff' in an object and weight is the force acting on an object due to gravity
• weight (N) = mass (kg) x gravitational field strength (N/kg)
• Earth's gravitational field strength = 9.8N/kg
• A free body diagram shows all the forces acting on an isolated object or a system
• A resultant force is when a force moves an object through a distance, energy is transferred and work is done on the object
• work done = force x distance (moved along the line of the force)
• 1Nm is equal to 1 joule of work
• The forces on an object in equilibrium combine to give a resultant force of zero

Stretching

• Elastic deformity means the object can go back to its original shape but inelastic deformity means they can't
• Force (N) = spring constant (N/m) x extension (m)
• The limit of proportionality is the…