Physics 2

• Topic 5- forces
• What is speed

  A scalar quantity- has only magnitude

  Doesn't have direction
• What is velocity


  Describes an object's direction as well as it's speed

  Vector quantity- has magnitude and direction
• What is the equation for speed

  speed= distance/time

  assumes that the speed is constant
• How do you draw vectors

  To add vectors, draw each vector as an arrow one after the other.

  The length of the arrow represents the magnitude of a quantity

  The direction of the arrow represents the direction of the vector quantity

  Pythagoras is used to work out the resultant force
• What is the equation for acceleration


  acceleration= change in velocity/ time taken
• What is displacement

  The distance an object moves in a straight line from a starting point to a finishing point. Vector quantity
• What is distance

  How far an object moves. Scalar quantity
• What is a contact force

  Happens when two objects are physically touching
• What is a non-contact force


  Happens when objects are separated
• What is a normal contact force (e.g.)


  When you push on a table, your hand doesn't move through it. The normal contact force from the table pushes equally on your hand
• What is friction

  Come about when two surfaces are touching and try to move against each other
• What is air resistance


  Comes about when an object moves through air and collides with air molecules
• What is tension

  The pulling force that a string or cable exerts when someone or something pulls on it
• What does a distance-time graph look like

  Motion at a constant speed is shown by a straight line

  If the line is horizontal, the object is stationary

  Speed can be measured by drawing a tangent and calculating the gradient
• What does a speed-time graph look like

  Motion at a constant speed is shown with a horizontal line

  If the object is stationary, the graph will run along y=0

  If the object's speed increases, the gradient will be positive

  If the object's speed decreases, the gradient will be negative
• How can the total distance of a speed-time graph be calculated

  Calculate the area under the graph
• What is mass


  A measure of the amount of matter that it contains and how difficult it is to change the object's motion- inertia
• What is the equation for weight

  weight= mass x gravitational field strength
• What is the centre of mass


  The point through which an object's weight appears to act
• What is a resultant force


  The sum of all of the forces acting on an object. The changes in an object's motion is caused by the resultant force

  Resultant force= mass x acceleration
• What does Newton's first law state

  The velocity of an object will only change if a resultant force is acting on the object.
• What does Newton's third law state

  Whenever 2 objects interact, the forces that they exert on each other are equal and opposite. If one object exerts a force on another object, then the other object must be exerting a force back
• What is inelastic deformation


  An object that will not return to its original shape when the force stops
• What is elastic deformation


  An object that will return to its original shape when the force stops
• What is limit of proportionality


  The point at which extension is no longer directly proportional to force
• What is the equation for Hooke's law

  Force= spring constant x extension
• What are the stages for investigating Hooke's law- practical

  1) Set up the apparatus as shown

  2) Measure the original length of the spring

  3) Hang different masses on the spring and measure the length of the spring in each case

  4) The extension of the spring equals the length with masses minus the original length

  5) Plot a graph with extension of the spring on the x axis and force on the y axis
• What happens when a spring is compressed

  Elastic potential energy is stored in the spring. The energy stored is equal to the work done when stretching it
• What is stopping distance


  The distance it take a car to stop in an emergency.

  Stopping distance= thinking distance + braking distance
• What is thinking distance


  The time it takes for a driver to react to a situation is their reaction time.
• What is braking distance

  The distance the car travels between the driver applying the brakes and the car stopping
• What factors affect thinking distance

  Distractions- children, phones

  Drugs or alcohol

  Tiredness
• What factors affect braking distance

  Road conditions- wet or icy

  The condition of the car

  Initial car speed
• How is work done on a car affected by speed

  The greater, the greater the braking force needed to stop the vehicle in a certain distance. More work needs to be done on the brakes to stop the car
• Topic 6- waves
• What are waves

  Transfer energy from one place to another without transferring matter. Wave motion can be shown by the vibrations of a spring or by water waves
• What is a transverse wave


  Causes the particles in the medium to vibrate at right angles to the direction of the wave's motion.
• What is a longitudinal wave


  Causes the medium's particles to vibrate in the same direction as the wave's motion
• What is the frequency of a wave

  The number of times a point on the wave oscillates per second

  frequency= number/time