Forces

• Displacement

  • Vector
• Time

  • Scalar
• Distance

  • Scalar
• Speed

  • Scalar
• Generally, scalars cannot be negative, but vectors can be, as a certain direction is positive
• Scalar


  Has just magnitude
• Momentum


  • Vector
• Energy


  • Scalar
• Acceleration

  • Vector
• All matter has a gravitational field, and attracts all other matter
• Vector


  Has magnitude and direction
• Speed is only velocity when given a direction, so thrown 10𝑚𝑚𝑠𝑠−1 is its speed but thrown 10𝑚𝑚𝑠𝑠−1 at 30° above the horizontal is the velocity
• Weight is the force exerted on a mass by the gravitational field, in Newtons
• Vectors

  Can be represented by arrows, with their size/length representing the vector magnitude
• A force is a push or pull that acts on an object due to the interaction with another object. All forces between objects are either: Non-Contact or Contact
• Imagine a car travelling round a roundabout at constant speed. While its speed is constant, its direction is constantly changing – so its velocity is constantly changing therefore it is accelerating
• The larger the mass, the stronger the field, the greater the attraction
• Mass


  • Scalar
• The weight of an object is considered to act at the object’s centre of mass
• Resultant Force is a single force representing the sum of all the forces acting on an object
• If more than one force act along a straight line, the resultant can be found by adding (acting in the same direction) or subtracting (acting in opposite directions) them
• Skydiver example: Forces that act are air resistance and weight. Initially, the skydiver has no air resistance and the only f
• Force


  • Vector
• Acceleration in free fall is due to gravity, and is the same as g, i.e. 10𝑚𝑚𝑠𝑠−2
• Imagine a ball thrown off a cliff, displacement is 0 at height of cliff, above the cliff the ball has positive displacement, and below the clifftop the ball has negative displacement
• Contact forces

  • Normal contact force
  • Friction
• Non-Contact forces

  • Electrostatic
  • Gravitational attraction
• Velocity

  • Vector
• In long answer questions, you may be able to decide where the “0” point of a vector may lie, for example you could set zero to be bottom of cliff, so the ball will never have negative displacement
• Weight = mass × gravitational field strength
• Elastic Deformation: The object returns to its original shape when the load has been removed
• One joule of work is done when a force of one newton causes a displacement of one metre
• As air resistance increases, the resultant force from weight decreases
• Resultant force when air resistance increases: 833 - 350 = 483N down
• Work done is when energy is transferred from the object doing the work to another form
• Acceleration decreases as air resistance increases, resulting in slower speed increase
• Work done against frictional forces causes a rise in temperature of the object
• Resultant force when acceleration decreases: 133N down
• Work Done = Force × Distance
• When air resistance and weight are equal, there is no resultant force