newtons laws and momentum

• newtons 1st law states than an object will remain at rest or move with a constant velocity unless acted upon by a resultant force
• newtons 3rd law states that when 2 objects interact, the forces they exert on each other are equal and opposite
• interactions can be gravitational, electromagnetic, strong nuclear or weak nuclear
• momentum = mass x velocity
• conservation of momentum: the total momentum of a system before an event is equal to the total momentum of the system after the event, as long as no external forces act on the system
• during a collision, momentum and the total energy are conserved
• if a collision is inelastic the total kinetic energy isnt conserved. the KE before the collision and the KE after the collision are different from eachother.
• inelastic collisions occur between two objects where some of the initial kinetic energy is lost due to internal energy being transferred into heat
• when there is friction present during a collision, the final speed will always be less than the original speed
• newtons 2nd law states that the net force acting on an object is directly proportional to the rate of change of its momentum, and is in the same direction
• newtons 2nd law: net force (directly proportional) to the rate of change of momentum
• force = mass x acceleration
• the area under a force-time graph is equal to impulse
• impulse = change in momentum
• young modulus = stress divided by strain
• Projectiles like cannonballs' travel distance depends on factors like the height of the cannon above the sea and the initial velocity of the ball
• In projectile motion, the vertical and horizontal motions of the ball are independent of each other
• Assuming no air resistance, the vertical velocity changes due to acceleration of free fall, while the horizontal velocity remains constant
• The horizontal velocity of a projectile remains constant because the acceleration of free fall is vertically downwards, and the horizontal acceleration is zero
• In a worked example of a cannonball fired horizontally from a clifftop, the time of flight and horizontal distance traveled can be calculated independently
• To calculate the time of flight, the equation s = ut + 0.5at² can be used, where s is the vertical displacement, u is the initial vertical velocity, a is the acceleration due to gravity, and t is the time of flight
• Acceleration


  The rate of change of velocity
• Average Speed


  Distance over time for the entire region of interest
• Braking Distance


  The distance travelled between the brakes being applied and the vehicle coming to a stop. It is affected by the vehicle and road conditions
• Displacement


  The direct distance between an object's starting and ending positions. It is a vector quantity and so has both a direction and a magnitude
• Displacement-Time Graphs


  Plots showing how displacement changes over a period of time. The gradient gives the velocity. Curved lines represent an acceleration
• Free-Fall


  An object is said to be in free fall when the only force acting on it is the force of gravity
• Instantaneous Speed


  The exact speed of an object at a specific given point
• Projectile Motion


  The motion of an object that is fired from a point and then upon which only gravity acts. When solving projectile motion problems, it is useful to split the motion into horizontal and vertical components
• Reaction Time


  The time taken to process a stimulus and trigger a response to it. It is affected by alcohol, drugs and tiredness
• Stopping Distance


  The sum of thinking distance and braking distance for a driven vehicle
• Thinking Distance


  The distance travelled in the time it takes for the driver to react. It is affected by alcohol, drugs and tiredness
• Velocity-Time Graphs


  Plots showing how velocity changes over a period of time. The gradient gives acceleration. Curved lines represent changing acceleration
• Velocity


  The rate of change of displacement. It is a vector quantity and so has both a direction and a magnitude
• Archimedes' Principle


  The upwards force acting on an object submerged in a fluid is equal to the weight of the fluid it displaces
• Centre of Gravity


  The single point through which the object's weight can be said to act
• Centre of Mass


  The single point through which all the mass of an object can be said to act
• Couple


  Two equal and opposite parallel forces that act on an object through different lines of action. It has the effect of causing a rotation without translation
• Density


  The mass per unit volume of a material
• Drag


  The frictional force that an object experiences when moving through a fluid