Forces (and interactions)

• What is the difference between scalar and vector quantities?


  Scalar quantities have size only; vector quantities have size and direction.
• What are examples of scalar and vector quantities?


  • Scalar: time, distance, speed
  • Vector: force, displacement, velocity
• What are contact and non-contact forces?


  Contact forces occur when objects are physically touching, while non-contact forces occur when they are separated.
• What are the only non-contact forces mentioned?

  Gravity, magnetic, and electrostatic attraction.
• How is force represented in diagrams?


  Force is represented by an arrow indicating size and direction.
• What is a free body diagram?


  A free body diagram simplifies an object to a single shape to make force arrows more obvious.
• What is the value of the force given in the study material?

  F = 110 N
• What is the value of N given in the study material?


  N = 275 N
• What is the mass given in the study material?

  m = 1000 kg
• How do you calculate the resultant force of two forces acting in the same direction?


  The resultant force is the sum of the two forces.
• How do you calculate the resultant force of two forces acting in opposite directions?


  The resultant force is the difference between the two forces.
• What is the resultant force when a car has a forward force of 275 N and another force of 395 N?


  The resultant force is 670 N.
• What is the formula for weight?


  Weight = mass x gravitational field strength

  • Gravitational field strength = 9.8 N/kg
• What is a resultant force?


  A resultant force is a single force that has the same effect as a system of forces on an object.
• How can forces be resolved?

  Forces can be resolved into two perpendicular components or combined into a single resultant force.
• What is an example of a resultant force with size and direction?


  108 N at 33° clockwise from the vertical.
• What do vector diagrams illustrate?


  Vector diagrams use scale drawings to illustrate how forces resolve and determine the resultant force.
• What happens if the resultant force is zero?


  If the resultant force is zero, the object will be in equilibrium, having balanced forces.
• How is gravitational force characterized?

  Gravitational force is a weak force.
• What is weight in relation to gravitational field strength?


  Weight is the force acting on an object due to gravitational field strength.
• How are weight and mass related?


  Weight and mass are directly proportional and produce a straight line graph through the origin.
• What happens when work is done?


  • Energy is transformed
  • A force causes an object to move in the direction of the force
• What is the definition of work done?


  Work done = force x distance.
• How much work is done when a force of one newton moves an object a distance of one metre?


  One joule of work is done.
• What is the relationship between joules and newton metres?


  1 joule = 1 newton metre (J = 1 Nm).
• What happens when work is done against friction?


  It causes an increase in the object's thermal store and the thermal store of the surroundings.
• How does work done against friction affect temperature?


  It increases the kinetic energy of the particles and therefore increases the temperature.
• What is temperature a measure of?


  Temperature is a measure of the average kinetic energy per particle.
• What is elastic deformation?


  • Causes a temporary change of shape
  • The object returns to its original shape when the force is removed
• What is an example of elastic deformation?


  The stretching of a spring beyond its elastic limit.
• What is Hooke's Law?


  • Elastic potential energy = \( \frac{1}{2} \times \text{spring constant} \times \text{extension}^2 \)
  • Work is done when a force stretches a spring
• What is the formula for elastic potential energy?

  Elastic potential energy = \( \frac{1}{2} \times k \times e^2 \)
• What happens when a force stretches a spring?


  Work is done and all the energy is transferred to the elastic potential store of the spring as long as the elastic limit is not reached.
• What is the formula for force according to Hooke's Law?


  Force = spring constant x extension.
• How is extension related to force in Hooke's Law?


  Extension is directly proportional to force.
• What is inelastic deformation?


  • Causes a permanent change of shape
  • More than one force needs to be applied to change the shape
• What happens during compression in relation to deformation?


  More than one force needs to be applied to change the shape during compression.
• What does Hooke's Law require as a practical?


  Hooke's Law is a required practical.
• What does the area under the graph represent in relation to a spring?


  • Represents the energy stored in the spring
• This law implies that when one object exerts a force on a second object, the second object simultaneously exerts a force equal in magnitude and opposite in direction on the first object.