Forces and their interactions

• What is a scalar quantity?

  Only has size (magnitude).
• Give examples of scalar quantities.

  Distance, speed.
• What is a vector quantity?

  Has both size and direction.
• Give examples of vector quantities.

  Forces, velocity, displacement.
• What is a contact force?

  When objects are physically touching.
• Give examples of a contact force.

  Friction, air resistance, tension, normal contact force.
• What is a non-contact force?

  When objects are NOT physically touching.
• Give examples of a non-contact force.

  Gravity, magnetic force, electrostatic force.
• What is a resultant force?

  Overall force on an object.
• What is the name of the force acting on an object due to gravity?

  Weight.
• What is the equation for calculating weight?

  Weight(N) = mass(kg) x gravitational field strength(N/kg)

  $W=$$mg$
• What is the centre of mass?

  The point on an object where the weight seems to act.
• What is work done?

  The energy transferred when a force moves an object.
• What is the equation for calculating work done?

  Work done(J) = Force(W) x distance(m)

  $W=$$Fd$
• What is the equation for calculating power?

  Energy(J) = Power(W) x time (s)

  $E=$$Pt$
• What is an elastic object (or elastic deformation)?

  An object which goes back to its original shape (after forces are removed).
• What is an inelastic object (or inelastic deformation)?

  When an object does NOT go back to its original shape (after forces are removed).
• What is the relationship between force and extension?

  Directly proportional.
• What does the spring constant(k) tell us about a spring?

  How stiff it is (greater the constant, more stiff it is).
• What is the equation for the relationship between force and extension?

  Force(N) = spring constant (N/m) x extension(m)$F=$$ke$
• How do you find the spring constant from a force-extension graph?

  Gradient.
• What is the equation for calculating elastic potential energy?

  Energy(J) = 1/2 x spring constant (N/m) x extension^2 (m)

  $E=$$1/2ke^2$