P2

• How can speed be calculated from a distance-time graph?

  The speed is equal to the gradient of the graph.
• How can the distance travelled by an object be calculated from a velocity-time graph?

  It is equal to the area under the graph.
• What is a scalar quantity?

  • A quantity that only has a magnitude.
  • A quantity that isn't direction dependent.
• What is a vector quantity?

  A quantity that has both a magnitude and an associated direction.
• How can a vector quantity be drawn and what does it show?

  • As an arrow.
  • The length of the arrow represents the magnitude.
  • The arrow points in the associated direction.
• Is a force a vector or a scalar quantity?

  • Vector.
  • It has both a magnitude and an associated direction.
• Give three examples of vector quantities.

  1. Velocity
  2. Displacement
  3. Force
• Give three examples of scalar quantities.

  1. Mass
  2. Speed
  3. Distance
  4. Temperature
  5. Time
• What piece of apparatus may be used to record the time taken for a very fast object to move a given distance?

  Light Gates.
• What is a force?

  A push or pull acting on an object due to an interaction with another object.
• What are two categories that all forces can be split into?

  1. Contact forces (objects touching).
  2. Non-contact forces (objects separated).
• Give three examples of contact forces.

  1. Friction
  2. Air resistance
  3. Tension
• Give three examples of non-contact forces.

  1. Gravitational forces
  2. Electrostatic forces
  3. Magnetic forces
• What is the name given to the single force that is equivalent to all the other forces acting on a given object?

  The resultant force.
• State Newton's first law for a stationary object.


  If the resultant force on a stationary object is zero, the object will remain at rest.
• State Newton's first law for a moving object.

  If the resultant force on a moving object is zero, the object will remain at constant velocity (same speed in same direction).
• If an object changes direction but remains at a constant speed, is there a resultant force?

  Since there is a change in direction, there is a change in velocity and so there must be a resultant force.
• When does an object fall with terminal speed?

  • When the upwards forces (air resistance) and the downwards forces (weight) are equal to each other.
  • No resultant force, so constant speed.
• What happens to the magnitude of air resistance on a falling object when the velocity increases?

  As velocity increases, the force of air resistance on the object will also increase.
• State the defining equation for Newton's second law.

  Resultant force (N) = Mass (kg) x Acceleration (m/s^2)
• State Newton's second law.

  An object's acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass.
• What is inertia?

  The tendency of an object to continue in its state of rest or uniform motion. It is an object's resistance to motion.
• What is inertial mass?

  • A measure of how difficult it is to change a given object's velocity.
  • The ratio of force over acceleration.
• State Newton's third law.

  Whenever two objects interact, the forces that they exert on each other are always equal and opposite.
• In a closed system, what can be said about the momentum before and after a collision?

  The total momentum before is equal to the total momentum afterwards.
• Explain how a seatbelt improves a passenger's safety during a collision.

  • The passenger must decelerate from the vehicle's velocity at impact to zero, so they experience a force.
  • This force is equal to the rate of change of momentum.
  • Seatbelts increase the time over which the force is applied, reducing the rate of change of momentum and therefore reducing the force felt by the passenger.
• Which quantity is equal to the force experienced in a collision?

  The rate of change of momentum.
• What does it mean if a force is said to do 'work'?

  The force causes an object to be displaced through a distance.
• Under what circumstances is 1 joule of work done?

  When a force of 1 Newton causes a displacement of 1 metre.
• What is power?

  The rate at which work is done.
• What can be said about the velocity of an object travelling in circular motion at constant speed?

  The velocity is constantly changing since velocity is a vector quantity and depends on direction as well as magnitude. The direction is continually changing and so does velocity.
• Explain the relationship between the force applied and the extension of an elastic object.

  The extension is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.
• What is meant by inelastic deformation?

  • A deformation which results in the object being permanently stretched.
  • The object doesn't return to its original shape when the force is removed.
• What is Hooke's law?

  Hooke's law states that the force applied is directly proportional to the extension of an elastic object.
• At what point does Hooke's law no longer apply?

  The limit of proportionality.
• What does the limit of proportionality look like on an extension-load graph?

  Where the graph stops being linear.

  
• What type of energy is stored in a spring when it is stretched?

  Elastic Potential Energy
• What is weight?

  The force that acts on an object due to gravity and the object's mass.
• What quantities does weight depend on?

  • The object's mass
  • The gravitational field strength at the given position in the field.
• What is meant by an object's centre of mass?

  The single point through which an object's weight can be considered to act through.