Physics

• A vector has a….

  magnitude and direction
• Give an example of a vector

  Displacement, weight, force, velocity, acceleration, momentum
• Give an example of a scalar quantity

  Mass, temperature, speed, energy, time, distance
• A scalar quantity has…

  A magnitude but no direction
• Vetor quantities are represented by?

  An arrow in the direction of the travel
• The definition of force

  A push or a pull that acts on an object due to the interaction with another object
• Is force a vector or scalar quantity? Why?

  Vector- it has a direction and a magnitude
• Force is measured in….

  Newtons (N)
• What characterises a contact force

  A force which happens when two objects are physically touching
• Give an example of a contact force

  Tension, friction, air resistance, normal contact force
• What does friction cause?

  The slowing down or stopping of objects
• Explain the result of air resistance acting on a skydiver as he falls through the air

  The air particles collide with the parachute and the skydiver, which causes the force of air resistance to act upwards
• Give an example of a normal contact force and explain it.


  A lamp on a table- the lamp exerts a downward force of weight on the table, and at the same time the table is exerting an upward force on the lamp.
• What characterises a non-contact force

  When the two objects are not physically touching, or they are physically separated
• Give an example of a non-contact force?

  Gravitational force, electrostatic force, magnetic force
• Explain gravitational force

  It attracts all objects to other objects. The gravitational force attracts the ISS to Earth, and Earth to the ISS
• Explain electrostatic force.

  The force between two charged objects. Objects with opposite charges experience an electrostatic force of attraction, whilst objects with the same type of charge experience an electrostatic force of repulsion.
• Explain magnetic force

  The force experienced by certain objects in a magnetic field.
• Define gravity. Include the type of force it is and what it does.

  Gravity is a non-contact force which acts as a force of attraction between ALL objects. It is a vector quantity
• What is mass measured in?

  Kilograms (kg)
• Is mass a scalar or vector quantity? Why?

  Scalar- it has a magnitude but no direction
• Does the mass of an object depend on where it is?

  No- the mass of a person on Earth is equal to the mass of that person on the moon
• Define mass.


  How much matter an object has in it
• Define weight. 


  The weight of an object is the force acting on it due to gravity.
• Does the weight of an object depend on where it is? Why

  Yes- it depends on the gravitational field strength of the planet or location they are in, for example the gravitational field strength of Earth is 9.8 N/kg
• What is the equation for weight?

  Weight = mass x gravity
• Give the units for the weight equation

  Weight = Newtons (N)

  Mass = kilograms (kg)

  Gravitational field strength = Newtons per kilogram (N/kg)
• What is gravitational field strength?

  The measure of the force of gravity in a particular location.
• What is the gravitational field strength of Earth?

  9.8N/kg (or 9.8 newtons per 1 kg of their mass)
• What is the weight of a 5kg object on Earth, which has a gravitational field strength of 9.8N/kg?

  5 x 9.8 = 49N
• What is the relationship between weight and mass?

  The weight of an object is directly proportional to the mass of the object

  weight ∝ mass
• How do we determine an objects weight?

  Using a calibrated spring-balance or newtonmeter
• What is the weight of an object of 100kg when on the moon and the Earth.

  Grav. field strength of Earth = 9.8 N/kg

  Grav. field strength of moon = 1.6 N/kg

  Earth = 100 x 9.8 = 980N

  Moon = 100 x 1.6 = 160N
• Define the centre of mass

  The single point where the weight of an object is considered to act.
• Calculate the resultant force acting on this car:

  Left: 10,000N of driving force

  Right: 4000N of friction force

  5000N of air resistance

  5000+4000 = 9000

  10,000-9,000=1000

  There is a resultant force of 1,000N acting to the left
• Describe what a free body diagram looks like.

  The object is shown as a point.

  The forces are drawn as arrows starting at the point.

  The length of the arrow shows us the size of the force.

  The direction of the arrow shows us the direction of the force.
• What is altitude?

  The height of an object above the ground.
• A plane is travelling at a constant velocity at a constant altitude (height above the ground.) Draw a free-body diagram to represent this. You should use the forces

  • weight
  • lift
  • thrust
  • air resistance/drag

  The weight must be equal to the lift to allow the plane to remain at a constant altitude (height), but they must act in the opposite direction. The upwards and downwards forces must be balanced.

  The thrust must be equal to the air resistance / drag acting in the reverse direction as the plane is moving at a constant velocity. The forwards and backwards forces must be balanced.

  
• What do we use to illustrate the resultant force acting on an object?

  Free-body diagram
• How do we calculate resultant force?

  Resultant force = large force - small force