A Level Physics

• Fractional uncertainty


  Ratio of the actual uncertainty to the measured value
• Percentage uncertainty

  Percentage form of fractional uncertainty
• Precision


  Measure of how well a result can be determined. Degree of consistency and agreement among independent measurements of the same quantity
• Accuracy


  Closeness of agreement between a measured value and a true or accepted value
• Distance

  Total length travelled by a moving object irrespective of direction of movement
• Displacement

  Linear distance and direction of the object from a reference point
• Linear distance


  Shortest distance from the initial to the final position of an object moved from one place to another
• Speed


  Rate of change of distance with respect to time
• Velocity


  Rate of change of displacement with respect to time
• Acceleration

  Rate of change of velocity with respect to time
• Equations of motion

  1. x = ut + 1/2 at^2

  2. v = u + at

  3. s = (u + v)t/2
• Drag


  Forces that oppose the relative motion of an object through a fluid
• Newton's 1st law

  A body stays at rest or it continues to move with a constant speed in a straight line unless acted upon by an external force
• Newton's 2nd law


  The rate of change of linear momentum of a body is directly proportional to the resultant force acting on it and is in the direction of the resultant force
• Newton's 3rd law

  If body A exerts a force on body B, then body B will exert an equal and opposite force on body A
• Centre of gravity

  The point at which the weight of the object appears to act
• Linear momentum

  Product of mass and velocity
• Impulse

  Product of the average force and the time interval over which it is applied
• Impulse-Momentum theorem

  The total change in momentum of a particle during a time interval equals the impulse of the net force that acts on the particle during the interval
• Head-on collision


  Collision where the directions of motion before and after are along the same line
• Elasticity of a collision

  Amount of kinetic energy conserved after the collision
• Friction

  Force that resists the relative motion or the tendency for relative motion between two surfaces that are in contact
• Tension

  Magnitude of the pulling force exerted by a string, rope, cable or chain on the object tied when it is pulled taut
• Hooke's law


  The magnitude of force exerted by a spring on a body attached to the spring is proportional to the extension of the spring from its natural length provided the proportional limit of the spring is not exceeded
• Upthrust

  Net upward force exerted by a fluid on a body fully or partially submerged in the fluid
• Moment of a force (torque)


  Product of the line of action of the force and the perpendicular distance from the line of action of the force to the point
• Couple


  Pair of forces, which are equal in magnitude but opposite in direction, whose lines of action do not coincide
• Work done by a force


  Amount of energy that was transferred to the body by the agent that exerts the force
• Kinetic energy


  Measure of the energy possessed by the body by virtue of its motion
• Energy can be converted from one form to another but cannot be created or destroyed
• Power


  Rate at which work is done
• Period


  Time it takes for an object in circular motion to make one complete revolution, or cycle
• Frequency

  Number of revolutions, or cycles, made per unit time
• Centripetal acceleration

  Acceleration which acts perpendicular to the velocity and always acts towards the centre of the circular motion
• Centripetal force

  Net force pointing towards the centre of the circular path, and is the vector sum of all the force components and points along the radial direction
• Newton's Law of Universal Gravitation


  Every point mass attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
• Gravitational field


  Region of space where a mass will exert a gravitational force
• Gravitational field strength

  Gravitational force per unit mass acting on a small test mass placed at the point
• Apparent weightlessness


  When an object exerts no contact force on its support
• True weightlessness


  When an object is an infinite distance away from any source mass or where the gravitational fields from the other objects around cancel each other