forces

• speed is a scalar quantity
• velocity is a vector quantity.
• scalar quantities: only have magnitude, do NOT have direction.
• vector quantities: have both magnitude and direction.
• displacement is the distance of an object moving in a straight line from its starting point to its finish point. it is a vector quantity.
• distance is how far an object moves and is a scalar quantity.
• non contact forces are when objects are separated; examples are: gravitational force, electrostatic force and magnetic force.
• contact forces happen when two objects are physically touching; examples of this are: friction, air resistance, tension and normal contact force.
• the area under a velocity-time graph is equal to the distance travelled by an object.
• speed (m/s) = distance (m)/ time (s)
• acceleration of an object tells us the change in its velocity over a given time.
• acceleration (m/s^2) = change in velocity(m/s) / time(s)
• if an object is accelerating at a constant rate… v^2 - u^2 = 2as (final velocity squared - initial velocity squared = acceleration x distance x 2)
• the mass of an object is a measure of the amount of matter it contains. the mass of an object is constant.
• inertia is a measure of how difficult it is to change the object’s motion. an object with high mass has more inertia than an object with a lower mass. it is difficult to move an object with a high mass (and high inertia), and once it is moving, the object’s motion is hard to stop.
• The weight of an object is the force that acts on the object when it is in a gravitational field. The weight (measured in newtons, N) is equal to the mass (kilograms, kg) multiplied by the gravitational field strength (newtons per kilogram, N/kg).

  ( W = mg )
• ( W = mg )
• • balanced forces mean no change in velocity.

  so long as forces on an object are all balanced, then it will just stay still or if it is already moving, it'll just carry on at the same velocity - so long as the forces are all balanced.
• a resultant force means acceleration.

  if there is an unbalanced force, then the object will accelerate in that direction.
• reaction forces.

  if object A exerts a force on object B, then object B exerts the exact opposite force on object A. every action has its equal opposite reaction.
• the bigger the force, the greater the acceleration or deceleration of an object.
• the bigger the mass, the smaller the acceleration
• to get a big mass to accelerate as fast as a small mass it needs a bigger force.
• the overall unbalanced force is often called the resultant force..

  any resultant force will produce acceleration.

  (resultant force = mass x acceleration)
• in most situations, there will be at least two forces acting on an object along any direction. the overall effect of these forces will decide the motion of the object - whether it will accelerate, decelerate or stay at a steady speed. if the forces all point along the same direction, the overall effect is found by adding or subtracting them. the overall force you get is called the resultant force.
• If object A exerts a force on object B, then object B exerts the exact opposite force on object A.
• When a force is exerted on an object, the object exerts an equal and opposite force.
• If a force is applied to an object, the object will apply an equal and opposite force.
• to travel at a steady speed, things always need a driving force to counteract the friction
• if an object has no force propelling it along, it will always slow down and stop because of friction (unless if in outer space where there is no friction)