Physics

• What is the metric system of measurements used today?

  The S.I. System, short for Le Systeme International de Unites.

  There are 7 base units of the S.I. system.

  Metre, kilogram, second, square metre, cubic metre, metres per second, and kilogram per cubic metre.
• What are the 3 fundamental/base units of measurement?

  Length (m), Mass (kg) and Time (hr).

  Fundamental units are the measurements that all other S.i. units are based on.
• What are the main 4 derived units of measurement?

  Area (m^2), Volume (m^3), Velocity (ms^-1), and Density (kgm^-3).

  * m^2 = metres squared

  A derived unit is a measurement that has been combined in any way with other measurements.
• What is the difference between fundamental and derived units?

  Fundamental units are the measurements that all other S.i. units are based on. Derived units are fundamental measurements that have been combined in any way.
• What is the conversion for units of length? (m)

  1000 - 100 - 10

  km - m - mm
• What is the conversion for units of mass? (g)

  ALL = 1000

  (tonne, kilogram, gram, milligram)

  
• What is the conversion for units of time? (s)

  7 - 24 - 60 - 60

  
• What is the conversion for units of volume? (L)

  ALL = 1000

  (ML, kL, L, mL) / cubic metre

  
• What is distance and how do you measure it?

  The total length an object has travelled, from beginning to end. It does NOT have a direction (scalar).
• What is displacement and how do you measure it?

  An objects change in position, measured in a straight line. It DOES have a direction (vector).
• What is the difference between distance and displacement?

  Distance is the total length travelled by an object, while displacement is the fastest route, measured in a straight line.
• What is a scalar quantity?

  A unit of measurement that has magnitude (size) only, represented by a number.

  Scalar quantities CANNOT be negative.

  E.g. Distance, time, volume, speed, mass, density.
• What is a vector quantity?

  A unit of measurement that has both magnitude (size) and direction. It is used to describe the position of one object/point in comparison to another.

  We use an arrow (on graphs) and compass bearings to show its direction.

  Vectors CAN be negative.

  E.g. Displacement, velocity, acceleration, force and drag.
• How do we calculate displacement? (same, opposite and other directions)

  Same direction = add displacements together

  Opp direction = subtract displacements from each other

  Other (not same or opp) = pythagoras theorem
• What is speed and how is it calculated?

  The rate-of-change of distance with time. Speed is scalar.

  Speed = distance ÷ time

  
• What is velocity and how is it calculated?

  The rate that an object changes position. It uses the unit metres per second (ms-1).

  Velocity = displacement ÷ time

  
• Where are time, displacement, distance and velocity on motion graphs?

  Time = x-axis

  Distance, displacement and velocity = y-axis
• What are the three types of motion graphs and what do they track?

  Speed graphs = distance with time

  Velocity graphs = displacement with time

  Acceleration graphs = velocity with time
• What is acceleration and what units does it use?

  Acceleration is the rate at which an object changes velocity.

  We measure it in metres per second per second, or ms-2.

  You can change velocity by speeding up, slowing down or changing direction.
• What is the equation for acceleration?

  Acceleration = final velocity - initial velocity / time taken

  
• What is 'g' in physics?

  The LOWERCASE letter 'g' in physics is the acceleration of a body due to gravity alone (acceleration of falling bodies). At sea level it is 9.8ms-2.
• Define terminal velocity


  The highest velocity reachable by a falling object.

  It occurs when... upward force = downward force of gravity.
• What is the first law of motion and what is it called?

  The Law of Inertia

  Every object persists in a state of rest or motion unless acted upon by an unbalanced, external force.
• What is inertia?


  The tendency of an object to resist a change in motion. Inertia is directly proportional to an objects mass.
• What is the second law of motion and what is it called?

  The Law of Mass and Acceleration (f=m x a)

  The presence of an unbalanced force will accelerate an object. The acceleration of an object is dependant on the net force acting on it, and its mass.
• Define mass.


  The heaviness of an object, measured in kg. Mass is directly proportional to weight.
• Define weight.


  The force exerted on a body by gravity. Weight (wt) is directly proportional to mass.

  wt = m x g
• What is the equation that expresses Newtons second law of motion?

  F = m x a

  Applied force = mass x acceleration
• What is acceleration dependant on? (2 variables)

  Acceleration is dependant of net force and mass
• In the equation F = m x a, what is acceleration directly, and indirectly proportional to?

  Acceleration is DIRECTLY proportional to net force, when mass is constant.

  Acceleration is INDIRECTLY proportional to mass, when net force is constant.
• What is the third law of motion and what is it called?

  The Law of Action-Reaction

  For every action FORCE there is an equal and opposite reaction FORCE.
• What does Newtons third law tell us?

  Newtons third law of motion tells us that forces come in pairs. We call these pairs action, and reaction.
• Is force a scalar or vector quantity?


  Force is vector. It has both magnitude and direction.
• What is a force?


  A push, pull or twist that acts on an object and causes it to change its velocity. They come in pairs, and are measured in Newtons.
• When is motion caused?

  Motion is caused by an unbalanced force.