1. General Physics

• A ruler is used to measure length for distances between 1 mm and 1 meter.
• The SI unit for length is in meters.
• To measure the volume of an irregular object you put the object in a measuring cylinder with water and measure the rise in water. The rise in water is the volume of the object.
• Time is measured using clocks or watches.
• The SI unit for time is in seconds.
• You can increase the accuracy for measuring any object by taking an average value. For example, to measure the period of a pendulum, you can take the time it takes to complete ten cycles instead of one and dividing the time by ten.
• A micrometre screw gauge is a tool used for measuring small widths, thickness, or diameters. It has a resolution of 0.01 mm.
• A scalar quantity has magnitude only.
• Example of scalar quantities include distance, time, speed and mass.
• A vector quantity has both magnitude and direction.
• Example of vector quantities include displacement, velocity, acceleration and force.
• Distance: The distance travelled by an object is the total length that is travelled by that object.
• The SI unit for distance is in meters.
• Speed: Rate of change in distance.
• SI unit of speed: meters per second (m/s)
• Speed is a scalar quantity.
• Speed can be calculated using the following formula:

  v = d/t

  where v is the speed, d is the distance travelled and t is the time taken.
• Velocity: Is speed with a given direction.
• SI unit of velocity: meter per second (m/s)
• Velocity is a vector quantity.
• Velocity can be calculated using the following formula:

  v = s/t

  where v is the velocity, s is the displacement and t is the time taken.
• Acceleration: Rate of change of velocity.
• The SI unit for acceleration is m/s².
• Acceleration is a vector quantity.
• Acceleration can be calculated using the following formula: a = (v-u)/t

  where a is the acceleration, v is the final velocity, u is the initial velocity and t is the time taken.
• For a displacement-time graph, the gradient represents the velocity.
• For a velocity-time graph, the gradient represents the acceleration while the area under the graph represents the displacement.
• Free falling: Free falling is a motion under gravitational force as the only force acting on the moving object.
• The acceleration of a free-falling object is always constant.
• On the surface of the earth, the acceleration due to gravity, g is equal to 9.8 m/s².
• Free-falling objects in reality are slowed by air resistance. Once air resistance is equal to the force of gravity, the object stops accelerating. The object is said to have reached terminal velocity.
• Mass: Mass is defined as the amount of matter in an object.
• The SI unit of mass is in kg.
• Mass is a scalar quantity.
• Weight: Is the force of gravity acting on an object.
• The SI unit of weight is in Newtons.
• Weight is a vector quantity.
• Weight can be calculated using the formula:

  W = mg

  or Weight = mass x gravitational acceleration
• Density is defined as mass per unit volume.
• The SI unit for density is kg/m³.